I think many social sites have tried to solve it, but in a world where anything is easily saved or screenshotted, it's still effectively a "universal room". Not to mention that properly implementing a form of role-based access control is a big ask for a lot users.

Not tying your IRL identity to online communications only solves one side of the problem. You can't use your anon accounts to communicate as yourself to family, friends, and colleagues and maintain your anonymity.

Not having accounts tied to IRL identity also allows AI bots to operate as equals to human users, which dilutes the quality of conversation in those spaces.

We've built an incredibly effective communications apparatus. It's a shame its only users are money-obsessed primates and the robots we've built in our image.