You do realize Bluesky also tacks on .bsky.social? (Though with a dot instead of a second @)

And even without other instances, ATProto already allows people to sign up using domains they own.

The closest you can get to using Lost_My_Mind as you Bluesky handle is by aquiring a domain like lost_my_mind.com. And that still wouldn't prevent someone else from signing up using lost_my_mind.net.

And that's before pointing out that Impersonation and mistaken identities isn't a solved problem on twitter, either.

Bluesky is succeeding because its a smooth and familiar experience that obfuscates away the complexity of how it works.

Absolutely nothing about how the ActivityPub network works conceptually prevents it from being an equally smooth experience, given the work were put in.

Your first six paragraphs hit the mark, but the following rant about the "username univerasility problem" ain't it.