You're missing my point. I'm saying, if you want to universalize college education to equalize opportunity between children raised in low-income families and children raised in high-income families --- a coherent cause, and one I happen to support --- you need to fix the systemic problems that keep low-income students from attending college, or free tuition will simply be another giveaway the government gives to people who don't need the help.
I'm not arguing against college (I think there are arguments against college as an opportunity equalizer, but I'm not making them). I'm arguing against free tuition for everyone as a vector for getting more low-income people into college.
If you want more low-income people to attend college, fix childcare first, so high-school age students aren't sacrificing class rank to take care of younger siblings and graduating high school into circumstances that demand they immediately find a wage.
Or, if you're dead set on applying pressure at college itself: means-test the benefit, so at least you're not giving billions of dollars away to families making six-figure incomes while families making less than $40,000 are sending their 17-18 year olds to 5 years of sporadic dead-end service industry employment. Because: "college is too expensive" is not the only reason that happens. There are plenty of extremely inexpensive community colleges that are vast improvements over 9 months working at the Sprint Cell Phone Store. But that's where low-income teenagers often end up.