So it might very well be, despite your analysis from 30,000 feet, that the charts would look very different if they focused mainly on the situation of those people who are not fit, by capability or inclination, to be techies.
This is at the core of it.
In the industrial economy (using IQ as a proxy for intelligence, flawed as it may be) the person with a 100 IQ could earn a middle class living, working in a number of different occupations that required a person with common sense who was willing to work hard.
Now, forget about it. The middle class jobs now require technical aptitude that your average 100 IQ individual can’t suceed at. When self-driving cars put all the 1.5 million truck drivers in america out of work, they are not going to become “coders” for cloud native technologies or go to med school. The ability isn’t there, no matter how much elbow grease is applied.