I understood that's what you've been talking about all along. I just disagree that it's such a big deal. yeah, I get that centralized services don't involve that step. I get that making choices before you know what they amount to can be quite hard for some people. but people still learn enough to choose a place to live, a bank branch to set up an account, a phone company, an ISP, and those choices often have a lot more impact than choosing a mastodon server. switching is so easy, especially early on, that I believe the solution for this non-problem is to state early on that, if you don't like the community of the instance you end up at, it's easy to move later, so don't sweat over it.
but there are other non-problem design choices that seem to make this more complicated, such as the conflation of instance and community, the lack of a "choose for me" option that picks an open instance at random (with documented caveats), or a "give me a short tour" that names a handful of instances for the new user to pick from to get started. wording that makes the choice less of a commitment than it seems to be taken as now is likely to lessen the apparent burden that leads to this misperception of difficulty. but the difficulty is a matter of perception. people have no trouble deciding whether to set up an account on twitter, or facebook, or instagram, or some or all of them, and hypothetical intercommunication possibilities between them wouldn't change that.