Interesting article, although I think looking at STEM as a single sector is a bit broad brush for my liking. There are shortages but it is in specific areas not across the board (for example, I don't think we have a shortage of people wanting to do academic research in STEM subject areas).

In areas where shortages exist they often aren't for entry level people anymore because the lack of recruitment is historical. In my area there appears to be a real dearth of engineers and scientists (industrial) in that middle ground between 'end of career expert' and 'start of career rookie'. A classic example would be myself, I've been in the business for 5 years yet I am being prepared to succeed a colleague who has been in the business for 30 years - where is the guy in the middle with 10-15 years experience?

What this means is that in more shortage areas there are really good opportunities for advancement with a few years experience, but only if you manage to get your foot in the door and that is not as easy as people are being led to believe.