LessWrong, and rationalists in general, probably have a blind spot relative to questions of civilizational inadequacy because those questions relate to political issues, and we don't talk about politics.

I don't think "we don't talk about politics" is true to the extend that people are going to have blind spots about it. Politics isn't completely banned from LW. There are many venues from facebook discussions with LW folks, Yvain's blog, various EA fora and omnilibrium that also are about politics.

I think we even had the question of whether people believe we are in a great stagnation in a past census.

I think the main reason is that I am 10x more pessimistic about the health of human civilization than most other rationalists.

How do you know? Did you actually look at the relevant census numbers to come to that conclusion? If so, quoting the numbers would make your post more data driven and more substantial. If you goal is to have important discussion about civilizational issues being more data driven can be quite useful.