The "STEM shortage" phrase means pay is too high for the very few STEM jobs; it means a shortage of income equality, not a shortage of warm bodies. There are obviously far too many warm bodies in STEM fields.
There is also a peculiar birth-death problem in academia where over the lifetime career of a professor, that prof should birth exactly one new qualified student to replace that prof. Otherwise we're dealing with a pyramid scheme. And one of the metrics of "success" of profs is how many qualified grad students they're birthing to provide short term cheap labor and long term hyper over supply of qualified candidates to be profs. We're merely seeing the breakdown of a pyramid scheme. One way to fix it is ban grad student labor. The undergrads, most of whom are going in to industry anyway, can be the lab rats. Or the prof can hire more postdocs.
Maybe not 100% but what fraction of PhDs are professors, maybe 3-5% at most, what about fraction of MDs working as medical doctors, I'm guessing its much much higher (with higher wages) since they limit enrollment in school and residencies (they don't rely on cheap grad student/post-doc labor).
There is also a peculiar birth-death problem in academia where over the lifetime career of a professor, that prof should birth exactly one new qualified student to replace that prof. Otherwise we're dealing with a pyramid scheme. And one of the metrics of "success" of profs is how many qualified grad students they're birthing to provide short term cheap labor and long term hyper over supply of qualified candidates to be profs. We're merely seeing the breakdown of a pyramid scheme. One way to fix it is ban grad student labor. The undergrads, most of whom are going in to industry anyway, can be the lab rats. Or the prof can hire more postdocs.