But it actually undermines your point. You're arguing that Twitter as it exists today is somehow inherently "democratic" and run in the public interest because some users subsidize others. And that's just incorrect; those users subsidize the others because it is in their financial interest to do so. They want their ads to show where the eyeballs are, that's all. If the economics changed and it suddenly became more attractive for the paying users (the advertisers) for Twitter to be an exclusive gated community, that's what Twitter would become. It is responsive to market forces, so in that sense it's a very capitalist institution.

Which is not a bad thing! I'm not saying that Twitter employees should run up the red flag and seize control of the means of production. I'm just saying that Twitter is a business, which is to say that it's an enterprise designed to enrich those who set it up. The fact that currently the easiest way to make that happen is to let some people use it free is tangential to that.