In my 2+ decades in the trades, the biggest problem is low pay and shitty bosses. Trade unions are absolutely packed full of people wanting to join them because they pay better, have more training, and offer paths towards advancement/pay/benefits over their hiring wage. But outside of the unions people pay crackhead wages then wonder why only crackheads want to lose 20 years off their life and wear out their body for customer service wages despite having a specialized trade experience and skills. Everyone who works in the trades also knows its a boom and bust cycle and they will get the shaft as soon as it is convenient for their employer which isn't a significant risk in many other industries and jobs.

And things get confused more when people only look at the top inflated wages for trade workers in the most expensive cities in the world, completely ignoring that most trade workers can't afford to live in those places and commute into the cities for their work and they almost never actually get offered the kind of wages that are advertised.

Real income in trades is up; that doesn't mean it's great pay, just up. Real housing costs have greatly outpaced that. It's the crazy post-2000 low interest boom-bust cycle that's wrecking the housing trades as a functional job. Trades are hugely oversubscribed during the boom, and the busts are too long to maintain the labor force.

If we want to build housing, we'll need a stabilizing force for that. I don't see a way to make that happen outside of govt intervention.