College is NOT an absolute fast track to employment. But it's an excellent reliable way to do that. Plus it's a fantastic place to find out more about yourself, meeting people, friends and for relationships. A lot of people have the college drinking perception. Which there is too much drinking, but there are a lot more ways to meet people in college where you're not drinking than in the working world.
Again just respect the work you and other people have done to get where we all are. Just to say "most people shouldn't go" is ridiculous. We want MORE people going. Show them how to do it in a financially responsible way. If that's too boring then stick to what you know.
I would even go so far to say that OP's anecdotal quotes from friends in "investment research" weaken his conclusion (i.e. I'm (100%) sure I'd be a millionaire if I'd started my current job 4 years earlier. But in order to get my current job, I must've gone to school for 4 years.)
For example, there's a subtle difference between these two stances...
your title: "A dirty secret: Most people probably shouldn’t go to school"
your conclusion: "So here’s a dirty secret of our times: you MAY just be better off not going to school."
If you're arguing that education could be faster and cheaper, I don't think that comes out in your post due to other distracting claims and anecdotes.
To me that just means folks need to be more thoughtful about the degree they select... after all, a quality, valuable education isn't something you're simply given, it's something you take.
Survivorship bias is real, but so is remarkably low return on investment. Its just harder to measure in people.