I think this is an important point to consider. For a long time, I kept thinking that the fediverse was going to be the answer to the problem of keeping separate accounts on every site (because most places are isolated/walled-in networks). It took me years to accept that “one account everywhere” isn’t what the federation model is about.
I wish there was such a thing, but that’s going to require portable identities/user accounts, and I don’t know why but that seems to be progressing at a snail’s pace with a bunch of stagnated RFCs everywhere (but please let me know if there is progress happening somewhere, I may be out of the loop). Once we have that, it’ll make the fediverse a lot more convenient, since then you should be able to log in to other instances with the same account.