Argument is a great way of forming relationships. The problem in modern times is that one person, typically the person such as yourself - endlessly confident in their flawless knowledge and determined to impose it on everybody, becomes belligerent when somebody doesn't simply graciously accept their impeccably perfect argument. That doesn't typically lead to good outcomes.

More generally, I think people have forgotten that two people - no less intelligent than the other - can see the exact same thing, evidence, or whatever else, and simply come to different conclusions.

Yes but i see argument as not about accepting that people come to different conclusions but actively trying to seek mutual understanding. There is a wrestling, a struggle, a fight to understanding, to communicating, that so many of us simply just run away from, and i believe it gets reinforced with cultural norms of avoidance and desire for "peace" instead of connection and deeper integration.