Yea that's a another giant can of worms. I work with some of the 'highest credential' people in the world (stanford/harvard/oxford with all the toppings). Although I don't believe the spread in intelligence is that great, I do believe the spread in education is absolutely staggering. Our lack of fluency in mathematics (can you understand the math in this paper?) That's an entry level math course at Harvard. Hell, when I was in High school, they didn't even teach calculus. I actually took calc 1-3 and diff eq in college, and that's all that was required for an engineering degree. It was a joke. Also, plenty of people who started in the engineering college found it too 'hard' because they never learned good study habits, and maybe some of them had a personality disorder and/or ADD that prevented them from being able to focus due to early life trauma, which is STILL not being taught to practicing psychotherapists (if you can even fucking believe that). Not to mention, the education and industry of doctors and healthcare, that's an entirely different rant (you would be wise to not mistake your doctor for some all-knowing/caring entity, chances are he's not well educated enough).

Anyway, I have too much shit to do to rant about this, but man it's scary and pretty overwhelming. If you really understood the spread in education right now in the world, it would absolutely floor you. The differences are MASSIVE. And so are the disadvantages it creates. Like you mentioned, most people aren't educated enough and just end up in some shit job working for less than 200k/year which is hardly enough to even live on, especially if you live in a big city.