Isn't that just "the World Wide Web"?

The reason these sites require login is because they also want to control the resulting conversations, whether for moderation (generous) or selling your data (more likely).

Announcements/political campaigning doesn't require feedback in the same way so no reason for them to use X, FB or anything else.

Seeing the state of most conversations on X or FB, I'm quite happy with limiting the general public's ability to broadcast to the world.