> But it seems dominated by the one software that is Mastodon, and it doesn't seem to have a universe of interesting connected neat social softwares sprouting up left and right.

There's quite a few activitypub software that plays nicely with mastodon, it seems to me. Like, Wordpress has an official activitypub plugin that allows likes, replys, following and all that. Lemmy, snac, pixelfed, bookwyrm, misskey, peertube, pleroma..

There's even work on distributed/custom recommendation going on.

I think it's fair to like either atproto or activitypub (I like both!), and bluesky certainly has momentum, but I don't think one can reasonably say the other side is not moving.