I think the best approach might be general subject-specific instances? Like, video.games with a main games community, meme community, then smaller communities for various games - or sports.social, with communities for each sport.

I feel like we’re going to end up with a particular community on a particular instance ending up as the “default” community for that subject, but it’d probably be better (in an ideal world) to have those on separate instances to maintain some degree of decentralization