"literally millions of open positions in the US economy": And almost four times as many unemployed people seeking work. Those open positions numbers are based on self-reporting, too, and they don't account for whether companies are actively seeking candidates, are offering a competitive salary, or are expecting reasonable qualifications. Lots of companies would love to hire busloads of experts at a bargain rate if they were available, but in the absence of a bumper crop of cheap geniuses they're happy to stand pat.

Surveys have shown that companies are having more trouble hiring people who have enough relevant experience than people with sufficient educational qualifications or technical skills [1]. To the extent there's a structural unemployment problem in the US, it's a bootstrapping problem -- too few entry-level positions in professional fields to supply the long-term need for experienced workers in those fields. This fits with my anecdotal observations of my 20-something friends -- their BAs won't even get them on the bottom of the ladder.

"who can't be bothered to master these STEM fields": Try: can't afford training in those fields. Try: can't get a job in those fields without years of experience.

[1]: http://business.time.com/2012/06/04/the-skills-gap-myth-why-...