The alternative to college education isn't going to look like a college.
What you end up with ends up looking a lot like a college. Now, we can talk about changing how funding for college works, but that's a separate discussion from changing the fundamental model, which I don't see as a practical goal.
There doesn't need to be one universal answer to this suggestion; it would be a boring suggestion if that were the case. Instead, you could look at the market for white-collar jobs and break it down looking for lucrative subsets, and then devise some kind of apprenticeship scheme.
If you could eliminate the 4-year degree requirement for HR directors, company controllers, purchasing managers, or jobs like that, replacing it with something tailored to the specific job, you could allow people to get an early start on a white-collar career while offering them opportunities later in their career to get something like an MBA or a JD.
But because the only current credible signaling mechanism we have is a 4-year degree, there is currently no good way to get the kind of job that might legitimately demand an MBA or a JD without first getting a degree in Russian Lit.
Any college replacement scheme is going to have to perform the same kind of filtering if it's going to be useful, and anything that performs this kind of filtering will be subject to exactly the same controversies the college system is subject to today. This outcome is because disparities in intelligence matter, and as long as we these differences exist and we need jobs with a certain cognitive threshold, we'll need something like college to indicate that certain candidates possess the needed traits.
It's important that it be very hard to lie about these qualifications, because anyone who could, would, due to the clear economic benefits of doing so. The only surefire way to determine whether someone has intellectual chops is to make him or her do something intellectual. That's what college is.
The good news is, we don't have to dig into that. All I'm saying is that it's calamitously expensive, across multiple axes (direct cost, opportunity cost, brittleness of opportunities) to assess capacity to perform the job of "HR Director" by looking for a 4-year degree.
I doubt that you believe a UMich Russian Lit degree is intrinsically an important qualification to work in HR (HR: one of the fastest growing white-collar jobs in the US, hence that example). I'm saying: that's a market inefficiency, and if you could find a way to arbitrage it, you could make a mint while making it possible for more people to get stable white-collar employment without reading Solzhenitsyn in a dorm room.