This is not the norm though. I wonder why people think countering something with an individual experience that's clearly distinct from the norm is a counter? It's not. His generalization is correct, your counter isn't evidence against it.
Part of the reason for the generational gap isn't just because of different culture. But it's also because where kids and adults are all day. Adults are at work, kids are at school. So the social connections, hierarchy and the dynamics are all completely different universes.
A lot of kids don't give a shit about grades because often that's not part of the social hierarchy at school. Money isn't even that huge either. It's when they get out of school all the rules change. That's why there's always this younger generational gap between teens and adults but less of a gap between say 20s and 30s.