If you want to know what's caused college tuition to skyrocket while the quality of that education has declined, I can explain it in three words: Government Student Loans.
As money started flooding the 'market' for post-secondary education there was more money than there were seats for students. Like any inflationary factor, more money meant costs would go up for existing products, in this case college diplomas. That's what's happened, with the costs for college rising far faster than the rate of inflation.
What's worse is that college was seen as the only path to success. But we know that it isn't true. We've seen multitudes of college graduates working menial jobs, jobs they could have had without spending time and money in college. We've seen people who took a more traditional path to success, like the trades, who have done far better than their college educated counterparts.
Basically what we've been sold is a bill of goods that ensures nothing...other than huge college loan debt.