It's not that there is a limited number of people capable of doing work in STEM, it's that the economy doesn't offer enough jobs
It's quite likely both.
There are absolutely people who can't (or won't) work with technology. And there are those who are qualified to do so who don't have the opportunity. Either way, opportunities for employment in the sector are limited.
I'm old enough to have seen a number of phases in high-tech career trends: highway construction (1950s & 1960s), nuclear power plants (1970s), defense (1960s & 70s) (a good family friend went through the trifecta of these three), consumer tech (1990s, 2000s), and Wall Street / technical trading (1990s - 2000s). Petroleum careers had their dark ages in the 1980s - 1990s oil glut. And there's the boom that never really materialized in biotech, which everyone and his kid brother's dog was pitching in the late 1990s / early 2000s, notably Larry Ellison and Tim O'Reilly.
It's quite likely both.
There are absolutely people who can't (or won't) work with technology. And there are those who are qualified to do so who don't have the opportunity. Either way, opportunities for employment in the sector are limited.
I'm old enough to have seen a number of phases in high-tech career trends: highway construction (1950s & 1960s), nuclear power plants (1970s), defense (1960s & 70s) (a good family friend went through the trifecta of these three), consumer tech (1990s, 2000s), and Wall Street / technical trading (1990s - 2000s). Petroleum careers had their dark ages in the 1980s - 1990s oil glut. And there's the boom that never really materialized in biotech, which everyone and his kid brother's dog was pitching in the late 1990s / early 2000s, notably Larry Ellison and Tim O'Reilly.