Like, one of the major points of the indie web is that you're no longer tying yourself down to a specific platform, but relying on the social features of Neocities works against that.
The problems with social media are a trade-off that we made in return for the (relative to the pre-social media web) massive amount of content we get to see and exposure we get on our own content nowadays. More generally: there is no easy way to gather and maintain social connections while truly owning your means of publishing. It's not hard, but it requires manual work, whether you're maintaining an RSS feed collection or constantly sharing links around group chats or maintaining webrings and link lists on your own site.
Forums, Discord servers, Neocities friends lists, they all make it way easier but any community requires lock-in of some kind, even on a small level.
I'm not saying that in a derogatory way, but rather I think a significant amount of people who engage with the indie web are only doing so because they want to be able to post things that look however they want, and are willing to learn HTML and CSS to do so.
That they're mildly locking themselves into Neocities by building their community on top of its social features (or, equivalently, in an indie web Discord server) is not a problem because the lock-in wasn't really an issue, the reduction of content down to a limited amount of images and text was the problem.
Cohost stumbled upon this unmet need with CSS crimes, and I suspect for a lot of folks if Cohost had some way of safely doing CSS without style attributes (maybe some trickery with making posts display within a Shadow DOM tree?) it would give them 90% of what they actually want from the indie web.
