The only people who honestly think there are a shortage of stem workers are those who aren't in stem.
Ask around, you'll find quite a few people like me.
https://en.wikipedia.org/wiki/The_Market_for_Lemons
So we end up with employers who don't want to pay top dollar in case they get a lemon, and competent developers who are either happy where they are or unwilling to work for lemon rates.
And have you interviewed candidates for development positions recently? It is depressing, and I say that as someone who catches flak about being too generous and letting too many "poor-quality" candidates through screens.
“We advertised this job for well below the going rate and didn’t get any applications, better outsource it!”