If there were a large, vibrant community of public squares, I'd very much agree with you; the problem is that the network effect means that there will only ever be 2-3 big ones. It's a form of natural monopoly if not monopoly-in-fact and that has to be accounted for if "the people" are to remain in control of their ability to exercise their rights.

So, one solution would be to foster an environment where Twitter et.al lose their power because they really CAN'T lock people in anymore and I would absolutely love to see such a future.

But unfortunately that isn't where we are right now and the incentives around us are all set up to ensure it never changes.