they have that right. By not working in the industry.
This argument assumes there's plenty of other jobs available and everyone's hiring. IME the only place that was somewhat true was the USSR and even then it wasn't quite how it worked IRL.
And even if it did, methinks it'd maybe work out if you're changing careers from waiting tables to janitorial services. Switching from marine biology to washing dishes is slightly different story (and a waste of a perfectly good marine biologist).
So yeah, you shouldn't do stuff you're not cut out for, but how about stuff you are cut out for and are good at -- except when the customer is a 300-lb walking heart attack who couldn't get to their junk without a boat elevator.