SolveIt: In the very thread there is someone who confuses this and you say, "My post was about classes, not "self-improvement communities". I'm very skeptical about the latter."
I'm not contesting that learning is improving but there is a class of things that people call self-improvement like "how do I not procrastinate". There is a common term for lone-wolf learning which is "self-learning". Not every improvement is learning either, what if you do a workout? If there are already two common terms why switch them? But then, when I was introduced to LW I saw a post mentioning "literal wireheads". Hmm.
But if you are simply talking about learning things by reading a book from home (vs a class setting where the professor barely explains the subject matter, rants about unrelated stuff for an hour then asks you to learn by reading a book from home and this is "motivating"), you can do it just fine. If you want to socialize, there are other ways to do so.
I'm not just talking about reading books. Gym classes, art classes, job training, toastmasters, etc. Moreover I'm not sure any activity aimed at "stopping procrastination" is worthwhile. It's just inherently unreliable woo. Go down a level and find a class or collaboration group on the object level thing you want to do. You'll end up doing it so much that it becomes effortless.
LW has a problem. Openly or covertly, many posts here promote the idea that a rational person ought to be able to self-improve on their own. Some of it comes from Eliezer's refusal to attend college (and Luke dropping out of his bachelors, etc). Some of it comes from our concept of rationality, that all agents can be approximated as perfect utility maximizers with a bunch of nonessential bugs. Some of it is due to our psychological makeup and introversion. Some of it comes from trying to tackle hard problems that aren't well understood anywhere else. And some of it is just the plain old meme of heroism and forging your own way.