There's NOTHING that you can learn in college that you can't learn out of college. Period. I challenge you to name something.
It isn't so much what you learn, as how you learn it.
Learning does not take place in a vacuum. I worked for 20 years to teach myself how to write, in my spare time, and I was pretty damned good at it before I ever set foot in college at the age of 41. But the one thing I did not and could not get was the benefit of peer review, and the benefit of experience. Sure, I could have found a writer's group, and a couple of times I did sit in on such groups. I found they knew no more, and usually much less, than I did about the art of writing, and I ended up teaching them instead of them helping me. That didn't do me much good, and in fact just reinforced certain bad habits I'd developed, as I had no one to teach me any better.
College taught me many things I had not yet been able to learn on my own in 41 years. (I'm 47 now, JSYK.) College helped me with subjects I'd given up on as a lost cause--like math. I didn't learn algebra until college. I didn't have anyone to make me learn it, which is very important with intimidating subjects. I had to learn it, like it or not, and I certainly didn't like it. But I went from a D to a B in just a year of instruction.
College exposed me to new ideas I had never considered. The exchange of ideas is extremely important to learning, as it's not about simply digesting what's gone before, but learning how to create what will come next.
College taught me discipline. There were places I had to be and things I had to accomplish, at specific times, whether I had the "want to" or not. For many people, this is a difficult skill to learn. It was for me, and college has helped me in this as nothing else in my life--parenthood and employment, for example--ever did.
College got me to read things I had always disdained before. I had never read a word of Hemingway until college, and only then did I realize what I had been missing. Likewise Melville, Frost, HD, Dickinson, and other Western classics I had always ignored as passe', old hat, unimportant. College taught me how to analyze these authors' works; I woudn't have begun to know the right questions to ask, nor how to find the answers, without college. I certainly didn't get it in high school. Discovering all of this, under the expert guidance of my professors, has helped my writing immeasurably.
College exposed me to new subjects I hadn't even known I had an interest in learning. Logic, sociology, anthropology, geology, weather and climate, 3-D art, 2-D art, sculpture, poetry (I'm a 5-time award winning poet, which I would never have been without college to encourage me and give me a place to get published) and much more were all opened up to me.
College helps you sift and organize what you're learning. Learning can be like setting out on a trip for a place you've never been, without a map. Which way do you go? What should you see along the way and what will just waste your time? Some side roads are beneficial, while some just take you further away from your destination. Are you sure, before you set out, that you know exactly which is which? A guide might be handy...someone who has been there before. Now where might I find that? Gee, I wish I knew.....
College is voluntary. No one will force you to go. You have to choose it. This says something about you to the rest of the world. You have to choose to finish it, too. This also speaks volumes. And you have to choose to do well, to complete your assignments, to earn a good grade...all of these things show others that you are serious, that your future means enough to you that you choose to better yourself, not just to sit around whining and waiting for people to hand you things.
College, above all, is not magic. You don't just walk in one door an ignoramus and walk out the other a blooming genius, with no effort or sweat required on your part in between. College is work; you get out of it what you put into it. Do people get graduated without having learned what they ought to have? Yep. I saw it with my own eyes. I've said it before--there are now, at this moment, people teaching English who can't properly use it themselves. This doesn't mean college was a waste of time and money for me, however. I got much more out of my 5 years of college (now edging into six as I change course) than I got out of the previous 41 years taken together. Mostly because I put much more into college than I've ever put into anything before.
You don't think college is worthwhile? Don't go. It's that simple.
But don't even try to disparage me because I did. Having read your posts, I know for a fact that there are things I know which, until and unless you go to college, you never will know.
And to quote Mr. Frost, that has made all the difference.