There have been many systems developed over the years for handling decentralized data storage, decentralized user identities, and decentralized decision-making. There are excellent options out there for all this stuff.

IMO the problem is that there's a huge "not invented here" problem, combined with a popular "ew, I don't want to be associated with that technology (or more accurately with the group behind that technology)" reflex that has nothing to do with the technology itself. So projects like the Fediverse keep reinventing the wheel over and over, and whenever a project manages to do something right it's rare for the other projects to abandon their own implementations to borrow from the best.