• Who made that rule? What potential bad consequence of someone you wouldn't call "genuinely troubled or ill" trying a talking therapy do you foresee?

• This article by Yvain on the difficulties with that distinction may interest you.

For what it's worth, the stigma of seeing a mental health professional has basically vanished over the last ten years. Sometimes being in therapy is even a status symbol...

A therapist isn't necessarily better than honest conversation with a good friend, but it sounds like you have trouble having that kind of conversation with your friends. Out of the different types of therapy, most of them have little evidence as to their efficacy, but there is a fair amount of evidence that cognitive behavior therapy works.

So I'll ask again -- why not try it? Being old fashioned isn't a very good reason.

Does your sense of being unlikeable have an impact on your self-esteem or lifestyle? To paraphrase something I heard about these things, it's only a problem if you think that it's a problem

Anyway, I second the recommendation of the Luminosity sequence, also this workbook; it covers a lot of the same material as talk therapy would but you can work through them independently, without the need to impose on anyone else.