Well, as far as I can see, the only options are for-profit, charity, and government-run. Of those, charity is undependable, and government-run has an obvious conflict of interest. For-profit worked for a couple of centuries in the form of newspapers. (Letters to the editor was the only part that was really a "town square", and that was subject to the whims of the editors. But for much of that time, there was competition between newspapers, so they tended to allow most viewpoints to be heard at least every now and then.)

So for-profit worked... and then it didn't, at least in the form of newspapers. Twitter also worked, but it's even-handedness is in question, and there isn't good competition if you don't trust it to be honest.