Agreed. We send too many people to college. I know many people who make really solid livings in the trades. Because they are not also forced to live in outrageously overpriced housing markets, they often have a higher standard of living than a Bay Area engineer.
Of course, we also educate too poorly in high school. I was always surprised in Switzerland how "well educated" my non-college climbing friends were. They commonly knew more about literature and philosophy than my college-educated friends in the US and held jobs mostly in the trades (and made comfortable livings).
'Your land must be a realm of peace and content, and there must gardeners be in high honour.'
'Not all is well there,' said Frodo, `but certainly gardeners are honoured.'
But I think the larger point is that mid-career coal miners and auto workers are going to be hard-pressed to successfully retrain in anything and get a job without having to pick up their families and move. There are so many obstacles to making the retraining scenario work.
Even if they do all learn a trade and become plumbers, Detroit doesn't need another 10,000 plumbers, nor does West Virginia.