The same is true for Bsky but people don't complain about it there. It asks you what server you want when you sign up, etc., which is what people complain about in the Mastodon journey.

Most people aren't on locked servers. By which, I mean the majority of mastodon users are on the .social instance which is the default when you sign up on the official app/site and is open to anyone.

Not an accessibility issue.