In the 90s the russians were the only ones with actual experience flying long term missions in space, the cooperation started with them allowing NASA astronauts to visit Mir. It was an exchange, not just a goodwill gesture, that was just how the ISS was sold to the US congress.

Now imagine if the US had been wiling to cooperate with them and made space debris avoidance part of the deal…

China was launching more rockets than the US for the past four years and is getting beaten this year only due to starlink. Mass to orbit is indeed a different story since most of the currently in service chinese LVs are smaller than their western counterparts.

ISS astronauts say they often enough don‘t see their colleagues all day, and the long term crew of tiangong is just 3 instead of 7, I think they‘ll be fine :) (well and of course people who actually have issues with this sort of thing won‘t get selected to be astronauts anyway).

It‘s also not quite comparable to sonething like a lockdown since they are busy working all day instead of having to sit around trying to kill time. And the actual total volume will be a bit bigger since there‘s usually a tianzhou and at least one shenzhou attached to the station.