That’s the thing, though. Bluesky gives you that option, too. And you could always just sign up with the one big official Mastodon server.
IIRC, they got hammered with new users back when Mastodon was more popular, and they couldn’t keep up (since every server is run on a shoestring). So, they put s moratorium on new accounts, forcing people onto other instances. That might’ve been what hurt adoption.
Not really. Bluesky has a server option, but it’s filled with their main instance by default and you can just ignore it.
Mastodon, on the other hand, doesn’t have a single entry point for registrations. Everything is more convoluted for the layperson.