Your post is all generalizations, with almost no specific examples. I think I disagree with most of the generalizations, but it would take an equally long post for me to explore why for each generalization.

In any case, you don't make any recommendations for how Less Wrong users should change their behavior. I might agree with those if you had made them. Here are some possible policy prescriptions based on your complaints:

• If you come across a cool concept Less Wrong is unfamiliar with, share it. I agree with this prescription.
• If you want to write about something, consider doing some scholarship and figure out what people outside Less Wrong have already said about it, and citing it. I agree with this prescription.
• Systematically assign Less Wrong users to consume other reading materials and discussion sites to find the best concepts and share them on Less Wrong. This seems like it might be promising, I don't know.
• Stop voting up posts unless they look like a typical EY sequence post. I disagree with this prescription. A typical EY sequence post is way longer than it needs to be and doesn't cite any studies.
• Try harder to write posts about topics EY covered. This seems like a silly heuristic. We should write posts about whatever topics are most profitable. If you want to argue that there are profits to be made in further exploration of specific topics EY covered, go ahead. If you think this is true for all topics EY covered, I suspect you are suffering from the halo effect around EY. The fact that the topic has been discussed in the past should, all else equal, make us less inclined to discuss it since more of what can usefully be said has already been said. Basic rationality posts on Less Wrong are as (probably) rare because basic rationality was covered a lot already in the sequences.
• Choose an accurate title for your post so people will not do too badly by assuming it says exactly what the title says. I agree with this prescription.
• Reread a post in full before linking to it. I'm not sure whether I agree with this prescription. Ideally every post would have a summary at the beginning, and it would be acceptable to read the summary only before linking if you'd read the full post in the past.
• Discuss politics more outside the comments. I'm not sure whether I agree with this prescription. Discussing politics for its own sake seems low value to me because Less Wrong doesn't have enough people to be influential, but it could be useful if it's going to be a rationality exercise or example somehow. I suspect EY's idea of using long past rationality failures as examples is a bad one because most people are way more familiar with contemporary rationality failures.

I recommend in future posts of this sort you attempt to take a random sample of Less Wrong posts and discuss them, so you will actually have evidence to support your claims.