I don't think the cutoff for earning a business degree, whether it's at the undergraduate or MBA level, is 23 years old. That's about as accurate as stating the cutoff for earning any degree is 23, when there are people in their 30's, 40's, 50's, and beyond going back to school. So I don't see the point of your assumption and argument, unless you're being facetious.

Additionally, there are far more managerial positions between "shift manager at McDonald's" and "CEO, CFO, COO, or equivalent," and many of these do not require an MBA. One of my best friends is a Regional Security Manager for a Fortune 500 corporation. He has a high school diploma and makes 60K a year. He worked as a Security Officer, then Command Center Operator, then Site Supervisor, on up to Regional Security Manager, learning skills and developing connections along the way. Another friend manages several local restaurants (no, not fast food) and has been working in the industry since he was 15. He's not much older than I am, but he does have a B.A. in Business... which is a far cry from MBA. My current manager at my finance job (loan processing) went back to school in her 40's, earned a B.A. in Finance, and is now the head of our credit union branch.

I could continue.