That's my opinion of Auth0 and similar services, no offense to Auth0, but people still use them.
As for federated auth... Twitter, Facebook, Google and Github authorizations seem to work okay-ish. Integration is rarely good. Login, User and Account are three different things, and people tend to conflate them poorly, this causes issues down the road in most projects.
Any standard can get adopted in two ways: either imposed by a dominant player, who can effectively force others to follow; or pushed by a wholly-independent 3rd-party that is completely neutral. Persona could not follow any of those strategies, and it withered, predictably.