A town square is usually a public project, maintained by the city on behalf of taxpayers.

This is more like a big private club.

Twitter is those public-use bulletin boards at the entrances of grocery stores.

(are those still a thing? Practically every store of any size had one in the 90s, at least, but I haven't paid attention and can't for-sure recall seeing one in years)

This is like a big private club that allows anyone to enter and has effectively taken the place of a town square, due to (among other things) lack of such a public project. It ought to be owned by the government, but we've privatized it.

What Twitter is an tries to be is pseudo-public space.

https://www.theguardian.com/cities/2015/aug/04/pops-privatel...

https://www.theguardian.com/cities/privately-owned-public-sp...

It isn't a town square - a town square is public. Twitter is a private organization. In this case, Twitter is the tavern. The Internet is the town square.

Is Facebook the town dilapidated mall full of geezers getting their daily walks?

No, it's the dilapidated mall full of geezers getting their daily walks that the Zuck creepily stares at for ad revenue