I think #mastodon growing so quickly may have held back the #fediverse. It's considered a de facto reference implementation for #activitypub, but it's a limited implementation. It doesn't support most Actor and Object types, it's client and server are tightly coupled, and it was designed specifically for microblogging. ActivityPub was an afterthought for it and it doesn't use it anywhere near its full potential.

Now every new AP project is following suit, developing a client/sever combination specifically to handle a single Object type, any enabling federation support on a project by project basis. We need a full AP server that's not tied to a specific client. It should support AP C2S API so a user can login to any client using oauth and handle different types. A user could use one client to create events, one to manage photos, and another to write notes or articles, and they'd all be tied to the same account.

Hopefully, people will get past thinking of Mastodon, Pleroma, PixelFed, etc and just think of the ActivityPub network. I don't think the fediverse will continue to grow without this change in philosophy.