57 different 3rd party apps is probably a good start. Mastodon has to be easy to on-board and it isn’t for someone with no technical understanding what domains, servers or instances are. To that group Bluesky makes sense. You are signing up for Bluesky. Try to onboard that group to mastodon and they don’t understand if they are on mastodon.social or mastodon.world or any other instance.
Why would they be on one of those fringe services with less users than bluesky? That’s what a non expert understands
The idea would be the servers would have shared ban/block lists and similar rules so that they can share the load of having open sign ups.
Basically a coop of instances to improve on-boarding. If you join the coop then you get added to the pool of instances that get assigned normies at random.
If the authentication was federated it’d be ideal as well but I assume this would be outside the scope of AP and would cause issues if you tried to post from your mastodon.social account from mastodon.world’s server for instance.