We don't have unlimited capacity for everyone who wants to make a good living doing $X to do be satisfied. They can hustle for a low-paying opportunity or they can just be told "no" by a central planner, hiring hall union, credentialing admissions process, etc.

That may solve an observer's concern about profit/exploitation, but it leaves the worker with strictly fewer options.

People not getting what they want is just as bad whether or not anyone else is benefitting at the same time.