So, whether "society as a whole starts paying for college now", is a separate discussion from "should we eat all college loans incurred so far".
State schools are already subsidized, look at the international tuition cost to find out the full on-the-books cost of tuition to the stare.
If the discussion is, Should we consider increase to 100% or close to it, the subsidy for state schools, some would agree. It will cause some disruptions, perhaps your space was available because someone else had decided it made no economic sense to take it, while now with free school, it makes sense for them to stay, and their grades were awesome, so that same seat is not available, and you can't get to the now more desirable free spot, and you are stuck in more expensive private school or not in college at all due to greater competition for the "free" spots that are more desirable. These things don't always work out exactly as you (or I) think they would. But I have seen a system that provided free college in public schools, but admissions are highly competitive, and there is a private option for those that want it. It's not a bad thing. I saw such a system while it lasted in Venezuela until 1999. (before Socialist/Theft-ocracy took over the country and crapped everywhere)
Here is a Wiki page to the elite school of the country:
Free for all that are accepted. Must score 95%+ on SAT equivalent for consideration.
This one is less demanding in admissions, but still considered a very good education, and also free like all the other public schools. My dad attended, and he might not have been able to if school was not free.
I prefer it to be affordable but not entirely free. I suggest that if we can get the subsidy and cost back to 1990s level of 1 month of minimum wage per semester, that was pretty accessible, and worst case if you stayed home and attended school Even if you got a loan for all state tuition, 4 years, that's only 8 months of Minimum wage owed... You could do a good chunk of the first 2 years in Community college (I did) and saved a ton too. That tuition was pretty much free for in-state. That's pretty close to free for the bargain you are getting. I prefer a portion of contribution is because it allows the state school to serve more students with the same money from the state.
In the US there has been a tradition of the states subsidizing University tuition,I'm unsure of the trend before the 1990s, but in effect it may have been similar, that the student contributed only a small portion of the total cost, and it added up to a symbolic portion of the total cost.