I think people are less well socialized than they used to be say 100+ years ago. Before you had 5+ siblings you constantly fought with growing up, so people learned better how to disagree.
It was also far more rare for parents to bend over backwards for you on your every whim and give in to the tantrums of their children. More people have learned that throwing tantrums gets them what they want, even in adulthood.
My parents had like seven or eight siblings apiece. Every kid grew up in the old days with twenty or more uncles and aunts and dozens of first cousins mostly in the same city. They grew up in a family filled with kids they had to learn to get along with. They spent all their spare time in unsupervised groups of kids where they again had to learn to get along, learn to socialize.
Now they grow up as a single child, or one of two. They might have half a dozen or fewer uncles and aunts and maybe two or three cousins who may or may not live in the same city. They don't spend a single minute of unsupervised play until they're in their teens.They go nowhere alone. They spend their time on the internet, or watching Netflix or playing video games or on social media.
They don't know how to get along with others because they've never had to figure it out.