My personal opinion is that "Global Town Square" is just nonsense that Musk made up. Twitter is not the first big privately owned social network and won't be the last.

The closest thing to that town square idea that actually exists is undermoderated cesspools like 4chan, which is not a good thing. Good moderation is simply necessary to have reasonable discussions/communities, and I feel like I believe that consistently.
I don't know if you think the (US) government should have that role, I think it would be a bit of a conflict of interest.

And I think what's happening to Twitter is unfortunate, but yeah the owner can do whatever he likes to it. However that still doesn't mean I have to approve of his choices or stay quiet about them either, that's not inconsistency to praise a company or its owner when they do good things and boo them when they do awful things. I'm certainly not going to say that he shouldn't have the right to censor whatever he wants, but it's still reasonable to complain about which things he chooses to exercise that right on.

The only reasonable alternative to these big private social networks I've seen is the fediverse, still private, but a slight bit more democratic in that if you disagree with your instance's moderation or administration, you can just use a different instance and usually still access most of the same communities.