Here's an example platitude:

“We often take for granted the very things that most deserve our gratitude.” – Cynthia Ozick

I read this, and it means nothing to me.

Yet I have a daily, involved gratitude practice. Give me a chance, and I'll wax eloquent about it. I believe it is one of the most important tools for my sense of well-being, having good relationships with others, and being an effective and moral person.

And I believe both that Ozick's platitude is objectively correct and that gratitude is a powerful and neglected way to increase human welfare.

Another way of stating your question is "how do we turn truths into motivations?" It's a topic that's related to the perennial discussion here about topics like akrasia, or curiosity and lack thereof.

My experience with gratitude and curiosity is that I can generate them within myself via specifiable and teachable actions. Convincing somebody to take my advice to the extent I think is necessary for them to discover the benefits is difficult.

For gratitude, my recommendation would be for somebody to write down three good things about every interaction they have, in person or via text, every day, indefinitely. They should also take a walk daily and strive to form conscious thoughts throughout that are expressions of praise and gratitude for both aspects of their life and for what they encounter on their walk. I believe that if they did this consistently, they would reliably experience a marked shift in their fundamental sense of self, relationship with the world, daily mood, sense of resilience, and more.

But I don't know how to convince somebody to commit to that.

Originality makes you take it seriously or engage with it more whole heartedly but I think the good property isn't "feeling original" per se.

Part of the problem about such tibits of wisdom that they are about big swath of experience/information and kinf of need that supporting infrastructure. When they are being developed or when they are prepared for transport they might be crystallised into single sentences or such but they need their prerequisities. That tip of the iceberg needs all that other mass to support that final insight.

Some times this is even semi-intentional. It can be beneficial to give someone an encrypted "spoiler" and then have them experience related stuff and then "get it". Good communication even has useful applications for the sayijng on different levels of understanding. Like "treat others as you would yourself" for a low level understanding can guide to introspect how you would feel in that situation. For more advanced understanding "in their shoes" considerations would come in that you can imagine if you were not you but had different upbringing or was in a particular situation (which is actually different to imagine how you would with your real characteristics act).

In preparing such "learning paths" it might be that some frasing is ultimately true but at low understanding face value suggests a wrong direction. For learning path needs having the impact be closer to zero rather than negative would be an improvement. And something that points in the rigth direction early might be confusing at higher stages. As there are usually many ways to frase insights over long time those that tend to lead to prosperous lives might be selected for. Some selection effects are stronger when transcending the learning period of a single human. If someone takes a insight and has perverse results then somebody else is likely to issue with that position/theorethical framework. Thus something that is "technically true" but requires to take many concepts in a very particular way is very fragile under cognitive diversity. But things that are robust under cognitive diversity are likely to be poor fits to particular cognition styles or stages.

One of the features of platitudes is that they are safe to be misunderstood. A person with only shallow understanding can be a host for the idea for succeful transport. But the idea itself is valuable enough that forgetting it would be punishing. Some other knowledge can rely on epistemic authority. But wisdom nuggets can be verified by the receiver over an unreliable network to be good ideas. Thus they need insight to "unlock". They are even so true and useful ideas that the method of proof can be left open.

Thus in a place where you would spit out a platitude the effectiveness can be increqased by making it particular or finding what in this particular life would function as the proof of the idea. The particulars will have different kind of evidentiary proof where a generic thought lacks it. "He would have wanted for you to live on" migth be generically or probabilistically true but "He would have wanted for you to keep kajaking" is dependent on hobby profile. And maybe some forms of living are genuneley less or more important for the emotional resosnance or genuinely why the lifes are important. ONe could try to lie about what the deceased would have wanted. But just asking about what the deceased did think probably gives multiple avenues for true particularised opinon how things should go post-humously.

In the book "the giver" a dedicated rememberer is asked whether a plane on a coliision course should be shotdown. When he advices that it should not be shot down and it later turns out they had a medical emergency the advice-seekers ask how did the expert know that would be the case. The answer was that he did not know, but knew how things go wrong if they go wrong and go right if they go right. So in a sense he did not posses information about this particular case and in one sense it was baseless speculation. On the other hand the opinion was informed by mountains of evidence about the patterns of that kind of life.

Off course the other side is that if you have very good data about what particular case you are in then trying to come up with robust and general generalization sis less attractive.

This is a big topic and I think both slider's "Part of the problem about such tibits of wisdom that they are about big swath of experience/information and kind of need that supporting infrastructure." and Christian's "It seems to me that the skillset towards which you are pointing is a part of hypnosis" are important parts of it. In particular, hypnotists like Milton Erickson have put a lot of time into figuring out how to best convey the felt sense that there is a big swath of experience/information in there that needs to be found, and how to give pointers in the right direction. Hypnotized people can forget their own name without understanding any of the supporting theory about how this is even possible, and religious people can live on commandments even though they do not grasp or have an ability to convey the wisdom upon which they rest. Knowing who to trust and how to believe things that one does not yet understand can be very important life skills, and it doesn't come naturally for those of us who like to "think for ourselves".

The reason Peterson can be so powerful in how he expresses these "platitudes" is that to him they aren't platitudes. He actually did the work and developed the wisdom necessary for these things to stand on their own and not drift away as a "Yeah, nice thought, heard that before". When you see the effects of people breaking the relevant commandments enough that you start to get a gut level appreciation of what it would be like if you were to allow yourself to make that mistake, it starts to have the same intrinsic revulsion that you get when trying to eat Chinese food after it gave you food poisoning the time before. It's a different thing that way.

If you look at someone who makes a living spouting feel good platitudes that they do not themselves live by or understand, how do they respond when challenged? How would you respond if you had tried to tell people to "clean their rooms" as if it were a solution for everything up to and including global warming, only to have BS called on you? Here's how Peterson responds. He does not falter and lose confidence. He does not back away into more platitudes to prevent engagement. He actually goes forward and begins to expound on the underpinnings of why "clean your room" is shorthand for a very important principle (in his view, at least, and mine as well) about how social activism is best done. He does it without posturing about how clean his room is and without accusing his accuser of having an unclean room herself. This part is a bit subtle as he makes no apologies for her behavior and his models do suggest unflattering motivations, but he doesn't go so far as to make it about her or about deflecting criticism from himself. He keeps his focus on the importance of cleaning ones room so that one can do good in this world and not be led astray by psychological avoidance and ignorance, and this is exactly what you would expect from someone who is actually onto something real and who means what they say. This engagement is crucial.

Even if "clean your room" isn't terribly informative or novel itself, his two minute explanation is more. Even though that's not enough, he does have books and lectures where he spells it all out in more detail. When even a book or two isn't enough, there's clearly a lifetime of experience and practice under there beyond immediate reach. You can get started with a YouTube video or a book, but back to slider's point, there's a big ass iceberg under there and you have to piece the bulk of it together yourself. The YouTube videos and books are as much an advertisement as they are a pointer. "Here are [short descriptions of] the rules he endeavors to live by, and the results are there to judge for yourself". When people see someone who practices what they preach and whose results they like at least in part, it creates that motivation to learn more of what is underneath and, in the meantime, to accept some of what they can't understand on their own when they can see that the results are there to back it up.

You can't just say "She's happier now in heaven" and expect words that are meaningless to you to convey any meaning. But when "She wouldn't have wanted you to be unhappy" is true and relevant and not just a pretense in attempt to avoid the real hurt of real loss... because the suffering they're going through isn't just plain grieving but also beating oneself up out of some mistaken idea that it's what a "good" husband would do... then absolutely those words can be powerful. Because they actually mean something, and you would know it.

When the meaning is there, and you know it, and you are willing to engage and stand up to the potential challenges of people who might want to push away from your advice, then even simple and "non-novel" words can be very novel and compelling thing. Because while they may have heard someone spout that platitude before, they likely have never heard anyone stand behind and really mean it.

It seems to me that the skillset towards which you are pointing is a part of hypnosis. Hypnotists like Milton Erickson spend a lot of time to come up with helpful metaphars for people and to communicate those in a very particular way so that they are likely to affect behavior.

Deliberate practice of coming up with metaphors is useful here. It lets you repackage existing knowledge in highly context relevant ways, and also is helpful for related skills in finding concrete examples when arguing abstract ideas.

The context and relationship in which aplatitude is used important to consider. In the cited example, the platitude may well be very helpful for the person to adjust a current narrative in their life. Platitudes may at times appear to work well to help when people when they feel stuck by leaning into agreeable generic wisdom which suddenly seems applicable to their current situation. I find it interesting to consider what precedes "ah ha" moments of personal insight that seem to transform perspectives on different situations.

I think it's healthy to be sceptical of popular psychologists.

Addressing the spirit of the question, I feel that you may find maxims to be a more useful device for communicating reason-based information. They have much in common with platitudes and clichés. But perhaps maxims offer some advantages. That which seems clever makes the everyday reader feel clever, something that is witty can be entertaining to read for those who may be otherwise uninterested. Benjamin Franklin can be cited as an example of someone who put together memorable maxims.

As far as I can tell, you do not really argue why you think platitudes contain valuable wisdom. You only have one example, and that one is super-vague. 

For me this post would be much better if you added several examples that show in more detail why the platitude is valuable.