Your ID doesn’t need to be tied to any given server. You can move around and change your “home” server at will. Or if preferred you could stand up your own server for your usage, hold your identify on there, and still engage with the rest of Lemmy / fediverse.
It’s less a design mistake and more a technical constraint. A users identify exists as, at a minimum, a database entry. That database needs to live somewhere that the various fediverse servers can talk to. But you have complete freedom in where that database entry is, and can change your mind later.
So it already doesn’t matter if you’re on beehaw, lemmy or some random mastodon or kbin server - they all federate with each other (to varying degrees but that’s a slightly different conversation)
Everyone going mad and many suggesting “if you have it use Safari instead!” when Apple implemented essentially this same thing quite some time ago in Safari 🤔
That said intentions are important. I have little faith that Big G’s goal is anything other than self servin.