Yes, everything in the Fediverse can talk to each other. But not everything in the Fediverse gives its users the same features locally.
If you're looking for something like Facebook, then Mastodon is crap because
- it's too much of a tryhard Twitter clone
- you're limited to 500 characters
- conversations are too loosely tied together from toots and more toots (as opposed to one post, many comments like literally everywhere outside old-school microblogging)
- no contact suggestions
- no dedicated profile fields, combined with no comparing your profile to other users' profiles for ranking in the directory (would make it easy to find folks with the same interests and/or who live near you and/or who have contacts in common with you)
- most importantly, no support for groups whatsoever, not even for groups outside of Mastodon
Lemmy is just as much crap because it can only do groups, and you literally can't follow/connect to specific users.
(streams) and Forte have everything you want minus marketplace. Hubzilla has everything you want minus marketplace and then a whole lot on top.
However: All three have the Eiger North Face of learning curves. There aren't any dedicated phone apps for either. None of them work with Mastodon apps. You will have to use the Web interface, full stop (all three can be installed as PWAs, but next to nobody knows that PWAs exist, what they are and how to install them, and literally everyone wants a native mobile UI in the style of their phones). And there are next to no public, open-registration (streams) or Forte servers.
So there's no "load app on your phone, name, maybe e-mail, password, there you go, default settings work perfectly for 99.9% of all users".
And I say this as someone who has been using Hubzilla as a primary daily driver since both before Twitter was bought out and before Reddit was enshittified, and who also has two (streams) channels.
At the same time, not everyone is looking for a new Facebook. Many only want a Twitter replacement for dumb-dumbs; it's actually Misskey or Sharkey although everyone's only ever being pushed into Mastodon. Others only want "Reddit without enshittification, but otherwise literally Reddit" which is Lemmy. Others want "literally Instagram, but not owned by Mark Zuckerberg" which is Pixelfed.
None of them would be happy on that utter feature monster that's Hubzilla. Hubzilla as a Twitter replacement is like you want a little boat with an outboard engine, and you're offered the Queen Mary 2 (admittedly, with a rather well-written user manual and a helpful community).