Before AI came, the doubling rate of workers in our industry was about two years. Even if it slowed down significantly in the last 3 years, that just means the average programmer quality moved from "fresh grad" to "established junior".

Growth rate alone forced the mean output to remain at beginner level. And then let's not forget that over the last decade+, the industry saw it fit to restrict almost all coding to juniors, and turned senior+ roles into a faux-management career track.