I get your intent - that people don't understand what federation means. But you're completely ignoring that we all live with federated email servers. Federated cell phone carriers, too, for that matter.
This is honestly not that different.
I 100% get what your intent is, but you seem to 100% not get that this sentence was completely false:
> I can sign up for an email right now with a dozen different services and not one will make me complete a mysterious task like "choosing a server"
And the same way that you can't "create your email account first, and then pick a server later," is the same exact reason you can't "create your Mastodon account first, and then pick your server later."
It's literally the same reason.
And you still seem to be completely rejecting that concept. As though this is "just bad UX." It's fundamental to how both e-mail and Mastodon work.
They can't "fix it," the way you wish they could.
Sure, they might come up with something, but it would be inherently worse at some really important things it's trying to do. It wants to be federated. Just like email. And you seem to not have any understanding of that.
AND to be -mad- at the people who are trying to help you understand. As though we're purposefully wasting your time.