Net bad. Too many degrees reduce their value in the market with poor job prospects. The extra years of education does not create an enlightened utopia.

It would be a net good if the people who went to college were changed in such a way that they stopped destroying value and started creating value.

That is to say, if college (more often than not) turned criminals into saints, and turned a welfare recipient into Erdos, then it would be an excellent investment for society.

But there's no evidence it does this, and it doesn't even do a better job than high school. You can learn more on youtube than you do in college.

So until then, it's a marketing racket that transfers state money into a few private hands- and the gov't goes around collecting for decades.