The ActivityPub protocol works by sending out every action on one server to any subscribed server. The subscribed servers save this data and make it available to the local users. If it worked the way you described, every server on the fediverse would store all the data from the whole fediverse. That seems wasteful.

I don’t like it either but the facts are the facts. Transitioning between technologies is always hard, especially if it isn’t necessary. Nat works too well.

That is very possible. IPv6 only is still problematic. There are still loads of servers without or with broken IPv6 connectivity. You could put cloudflare on front of your server and get an IPv4 address that way.

That’s a generic top-level domain. It is not associated with any country. It belongs to “Identity Digital Inc.”.