If you compare what the big resort towns rely on from the mountain twenty years ago to what they rely on now, you'd find everything you claim to be patently false. Every single town has diversified well in advance of the resorts slowly becoming less of a thing.

Lets also address that those jobs were never guaranteed and the resorts outsource as many of them as they can to seasonal foreign workers that don't "need" them. Those jobs are rapidly becoming obsolete for the towns and the people to survive. And towns that solely exist due to the mountains will move on like many others have.

Those locals will be fine, their resume is longer than you can ever imagine.