This is an underrated point; I think your larger message, that cooperation isn't dying, is likely true. I think I have the tendency to focus on the problems that are growing (or continue to exist) without noticing areas where there is progress and my comment was a reflection of that. And I agree that it is good that we have started to have these conversations.

But I also think there is something to be said for the point the OP was making: human systems simply don't function as well at scale. Or stated more precisely: humans are better at being prosocial in smaller groups than they are in bigger groups. There are a lot of reasons why this might be the case (see for example [0], [1], [2], [3]). As we scale our society to be more and more global, I think we are going to need to reckon with this at some point.

[0] Not having enough interactions for tit-for-tat to function as a strategy (https://en.wikipedia.org/wiki/Prisoner%27s_dilemma#The_itera...)

[1] Inability of humans to hit the requirements for a sense of community in very large social networks (https://en.wikipedia.org/wiki/Sense_of_community#Membership)

[2] Not having enough interaction between individuals to encourage reciprocity and cause feelings of guilt (or shame) when an individual is muddying the commons (https://en.wikipedia.org/wiki/Tragedy_of_the_commons)

[3] https://en.wikipedia.org/wiki/Dunbar%27s_number

Maybe there is some limit where there's too many people for that to occur. I feel one of the necessary conditions is the population needs a cohesive belief system (at least in certain areas). For example, if you have a large population that doesn't believe in science but in the invisible hand of god, and a large population that is scientific humanist then I don't think any system will cope with that - there is very little common ground. If everyone is educated and believes in a rational universe then it makes things a lot easier.