We still have festival type experiences: concerts, street festivals, gatherings in a park, church, etc. None of them particularly look like the bus.

For one, when and where this was the case, it was probably once a year or so.* Not daily or weekly.

Furthermore, the "voluntarily" bit plays a big role as well. If I were to go to a big festival (as you can guess, I wouldn't), then I guess I would be fine with the people. But that's not the same as commuting IMHO, where I'm together with lots of people involuntarily.

* it's an interesting topic actually, so if you have any sources, I'd like to read them.

We have anthropological evidence that humans lived like sardines in a can 24/7? Where?

Ah yes, that natural many-thousand-year-old massive festival tradition we all know and love: the twice-daily subway ride. Good comparison.