My college degree from Syracuse in 1989 did little to lift me into the middle class.
However, my (CDL)Commercial Driver License from 1996 opened plenty of doors I never knew existed that lifted me into the middle class.
Having a sheepskin may offer entry job opportunities early on in one’s career but you’re right, after that its not so much what you know as what you produce that allows you to enter the middle class. A degree is an accomplishment, but its just one accomplishment in a long string of producing results and achieving outcomes that matter that propel your career. Production in any field generally leads to success.