I think federated projects really look at federation as an add on to their platform, not a core feature. E-Mail did this well where everything was automatically federated by default (I.e you can send email from anywhere to anywhere for the most part) whereas some fediverse software, specifically lemmy, require that federation be enabled (and I believe you choose to federate with servers on a per-server basis).
Where I work we're working on a solution to this where your identity remains sovereign between servers [1]. We currently have a Twitter-esque microblogging demo setup [2].