Stop "open enrollment" at public universities and watch the laws of economics kick in.
Of course, all hell will break loose when people who barely graduated high school or got GED and those who "aren't good at taking tests" can't get into college, but who cares?
Not that people who go to vocational schools do so because they can't cut the academics, but we certainly need more plumbers, AC techs, and god knows we need more dental hygienists than we do half of the majors offered at colleges.
At the same time, we could use changes to the system to generate more American doctors so that the AMA doesn't have a stranglehold on medical costs.
What I see as a huge waste is when someone gets a four year degree in something useless just so they can get to graduate school where they learn something useful. The other thing is when people spend years of study and big bucks for what I call "credentialization". Many of the occupations (Like school superintendent) do not have any rational requirement for a Phd. The job of superintendent was long an elected position, one filled by a person with a background in management or business rather than a degree in psychology or the Application Of Cosmic Bullshit. But the require a Phd because it makes the job look more important and worthy of a $300,000 salary, contract, and golden parachute.