The problem today is that there are a lot of people who pursue degrees with little regard for the cost and the applicability of the degree they're pursuing. If they do that now, when they have some skin in the game, how will that improve if college is "free". I think you'll see more people getting degrees in fields that have no job market. Sure, they don't have debt (the rest of us will foot the bill), but they have no job prospects either.
The people I see on Facebook and other social media complaining about the cost of college and the job prospects they have all have one thing in common: they bought into the "pursue your passion" lie and came out of college with a degree that they can't use.
If taxpayers only agree to foot a much smaller bill, universities will be forced to cut all the frivolous stuff and get serious about education. I'm all for taxpayer-funded college but not at the prices these colleges charge at present. You don't see college football and all the other non-educational nonsense in Germany (using that because it's an example of a country with a free college system). "Free" college should pay only for classrooms and labs, professors and TAs - no dorms, meal plans, overpriced textbooks, sports or extra-curricular activities (unless paid for by students or donors), huge admin staff and the rest.
I saw something at one point that said that colleges now are luxurious compared to the colleges of 30/40/50 years ago. The implication there was that once students had easy access to student loans, state schools in particular no longer focused on being cost effective. Anecdotally, I live in a town with a state school (Illinois State), and the apartments that have sprung up on campus over the past 10-15 years are insane compared to what I saw in college. Flat screen TVs in every unit, pools, etc. This is probably the most extreme example, but there are many similar: https://thelodgeonwillow.com