Also if you're into human biological differences and heretical things like IQ, the bell curve bar for "can farm instead of hunter gather" "can factory instead of farm labor" is very low, like IQ 70 or something. You don't need an IQ of 120 to put a nut on a bolt on an assembly line.
However, lets say all the jobs with IQ below 120 are replaced with an IQ 120 AI or similar automation via the efforts of over IQ 120 engineers...
Most of the population is physically unable, as best we understand, to ever obtain a MSEE or a PHD in computational fluid dynamics. It doesn't matter if we have 100M job openings for people with advanced CS degrees no matter how much we pay them, with only 300M people in the country the bell curve says we can't find the warm bodies to staff them.