Imo part of the problem with mastodon, at least in my experience, is that it's sold as a twitter replacement while still being devoloped and largely populated by people who don't like twitter (because it's too "toxic"). This means that you can't really have the twitter experience on mastodon by design so people coming from twitter mostly wanting to get away from musk bounce of. Bluesky has been a more successfull twitter replacement and I think that's largely because it basically is twitter with feeds.
I think that mastodon should either commit to being more like twitter (which it is propably too late for at this point since I don't imagine that their current userbase would be into that) or people should stop trying to make it the new twitter and instead let it be it's own kind of different thing.