I've been SLOWLY getting into the Fediverse for a little over a year now. My biggest gripe has always been discovery and availability. I feel like there is a lot more effort required to find people/communities I am interested in. Then if/when I do find them they are often not very active.
So yeah I'll say what everyone else is saying that UX needs some work. I used Lemmy for a while last year and just couldn't get used to the interface, I'm not Feddit and like this interface more. But it could use some work on mobile imo.