From a UX perspective federation has been absolutely bungled. Twitters greatest trick was to cause an exodus before the alternatives had reached maturity, though I imagine the demand has pushed them further than they would be otherwise.
IMO BlueSky is by far the best Twitter replacement, insofar as you can just use it like Twitter but it is built on an open protocol, allowing you to run your own server if you wish but with zero interoperability friction or worrying about servers on the actual client. Also it has already started basic bridging between threads and mastadon, its custom feeds in place of algorithms is genius and stackable moderation is the most compelling solution I’ve seen to the core complaints and concerns over modern social media.
And it’s independent, transparent and run by intelligent, passionate people. And, very importantly, Jack Dorsey has nothing to do with it!