Most people are (somewhat) stupid in their early 20s. I don't disagree that not everyone belongs in university, however, most people don't realise that until it is too late and are already in debt.
Free higher education works well in the European countries that offer it.
What better investment could a society make than allow someone to pursue a field they are passionate about, and letting them start life with a clean slate? I'm by no means a socialist, but I think university should mostly be free.
The only thing (student) debt does is tie someone down. To a lifestyle or employer that they actually should have no loyalty to.
Tax brackets don't need to rise, resources just need to be moved from alternative things (i.e. military spending).