It was 10% of the US population who went to college before the GI bill, which then doubled to 20% over a decade following the war. Now >50% have post secondary. 70% attempt post-secondary after high school
Before WW2 only about 40% of people completed high school, now it’s at 90%
Those numbers actually back up the point. The jump in education after WWII happened during the biggest boom years the US ever had. The rise to 40 percent college grads happened much later, during globalization and offshoring. So the slowdown is about the economy changing, not people getting more education. It is just a bad correlation.