What would happen to all those Liberal college professors if unqualified people stopped going to college just because it didn't make economic sense?
Actually, more to the point (from my perspective) is “what would happen if we instituted a national ‘qualifications’ exam for most college majors, and moved to more of an online education system”. For many things, Europe has had these types of exams. You take them when you're ready, and you have to pass to be given credit for training and competency in that field.
This would: 1) Make education much cheaper and accessible; 2) Diminish the automatic acceptance of the meaning of a degree from any institution (it wouldn't matter if you went to Harvard etc.; only that you showed competency when tested; 3) Allow people who can't afford to go to school without simultaneously having a job to work online at a pace that matches their available time; 4) allow people to get real world job experience while getting an education; 5) force universities to compete in a much more real world. Etc....
I know some people don't do well on standardized tests, but we have the technology to have very diversified testing, with interactive problem solving etc. For so much of university education it doesn't matter where you are. You may be lectured by graduate students or teaching assistants, the professor might be a marginal educator and have their position on the basis of grants they've gotten, or their publications. Much of what you learn during the years you spend at a university is very much independent of the time you spend in a classroom.