I respectfully disagree with some of your points. The benefit of a Twitter clone that is federated (or more precisely, a Twitter clone that supports activityPub) is that the users of said Twitter clone can see content from and interact with users who aren't on said clone, but another platform that supports activityPub. And conversely, I can see content from said Twitter clone without necessarily having to be on it, as long as I use some activityPub platform that fits my taste.
This provides a lot more choices. I can choose a platform with the best user experience for my taste, without any regard to privacy and moderation. That would be completely fine. Conversely, another person may choose to search for an instance based on their specific moderation, topics, privacy, or other preferences. Another person may even self host their own instance. All of those can interact with each other, and that is what makes it nice.