The weird thing is that people on mastodon mostly go along happy with their feed. Those that have found the problems too much bounced or just learnt to tolerate it. One thing that may fade away is the idea of running your own personal instance. I get the feeling that some don't find it to be entirely worth it. There are "relays" though, which are commonly used, and basically feed in content from major instances as though you're following a bunch of people there. I don't really know how that goes though.
With lemmy (and kbin too), yea, it certainly feels like it's not far from being kinda "done", at least as a version "1.0". Scaling up to many more users is likely to surface more issues though. But we've got many apps and alternative front ends, a somewhat stabilising API and months now of mostly working as intended.