Making it harder to get a student loan is hardly "outlawing" anyone from going to college. Schools would still give scholarships. Plus, tuition would almost certainly go down. Right now they can charge as much as they want because banks are will to lend whatever colleges charge. If all of a sudden people stopped buying their product when they raised the price too high then tuition would come back down to what it was only a few decades ago.
Even if fewer people ended up going to college it wouldn't limit opportunity. If anything it would likely make it easier to get ahead. Fewer jobs would require a college degree - there wouldn't be enough applicants who have one - and we'd likely see alternatives to college become more popular and widely respected, which would give high school grads more options for how to get started with a career.