I think it was some variant of the Typical Mind Fallacy, albeit one based not only on my own preferences but on those of my friends (though of course you'd expect that I'd associate with people who have preferences similar to mine, so this does not make the fallacy much more excusable).

I think the main belief I've updated based on this is my estimate on the prevalence of my sort of individualistic, suspicious-of-groups, allergic-to-crowds, solitude-valuing outlook in the Less Wrong community, which I have adjusted strongly downward (although that adjustment has been tempered by the suspicion, confirmed by a couple of comments on this post, that people who object to things such as rituals etc. often simply don't speak up).

I have also been reminded of something I guess I knew but hadn't quite absorbed, which is that, apparently, many people in aspiring rationalist communities come from religious backgrounds. This of course makes sense given the base rates. What I didn't expect is that people would value the ritual trappings of their religious upbringing, and value them enough to construct new rituals with similar forms.

I will also add that despite this evidence that way more people like rituals than I'd have expected, and my adjustment of my beliefs about this, I am still unable to alieve it. Liking ritual, experiencing a need for and enjoyment of collectivized sacredness, is completely alien to me to the point where I am unable to imagine it.