Well, even back in my grandfather's day (he was a millwright for Ford) working on the line required more mental skills than most people realized. Remember when Elon Musk finally gave up trying to 100% automate his factories? He said "we undervalued the abilities of humans."

If manufacturing cars is so complex you can't train monkeys, or build robots, to do it, how much harder must it be to make chips?

Making things that small, that precisely, repeatably, profitably, by the millions and billions, is spectacularly complex. And with each process node, the complexity grows even faster than Moore's law does.

Eventually, it gets to the point that even to tell somebody how to do something, you need to do it using the language of advanced physics, the kind of physics which requires you to spend studying 60-80 hours a week, for 5-7 years in grad school to learn. As the gen-X proverb goes, reality bites.