Woah, this is the logic that is getting us in trouble!
66% of people already go to college. Of those who go, only 50% graduate. So...
1) Does "college" matter or does learning a marketable skill mater? If we had 100% college enrollment and completion but everyone was getting a degree in native American studies, would we somehow be better off?
2) At what level of enrollment does it become more cost effective to simply extend high school 2-4 more years and just consolidate it?
College in its present form is in trouble because the lions share of college attendees are; white women, taking non STEM degrees, taking on federal loans, and having a lower workforce participation rate at the end of it.
College is about learning, not about what a huge chunk of it has become; safe spaces, community outreach, nice dorms, cafeterias, dating, fitness centers and generally taking a hiatus from life. We really need to redefine college in its present form, it is no longer what it was 50 or 100 years ago.