I tried Lemmy for a bit and found it to be nothing more than a tiny Reddit clone. And I don't mean just the software aspect of it, rather the content and moderation.
Reddit recreated the social structure of Usenet. Shared infrastructure, but the subreddits managed themselves. Topics, threads... all similar to Usenet. Better multimedia support, of course.
Even the phenomenon of anonymous posters (because accounts didn't require an email for a long time), flames, crossposting... all very like usenet.
Usenet preceded modern social media so the current discussions about who owns content didn't apply.
Reddit was remarkably open in the beginning. Anon accounts, light moderation, open API... it's when they decided to try to extract more value that it became really shitty.
Discoverability and fragmentation seem to be the problems on Lemmy. Groups are small (not really a problem, the smaller subreddits with active and engaged people are better IMHO) but it's really difficult and high-effort for groups to form. Reddit did seem to have that part working well. I think people have gone into Discord (which sucks/I cannot stand).
I hope the fediverse somehow wins but it doesn't look likely any time soon