> but until a person’s salary exceeds the value they bring to a firm, there will be other firms willing to pay more and attract that talent

This is false. Supply and demand is a factor. I could clean the toilets at the office, if janitors were in short supply my boss might setup a rotation schedule - nobody wants to but it must be done and so he would pay me. However because janitors are cheaper than me he doesn't. This isn't just theoretical - McDonald's mostly has the crew clean the floors - janitors make more money than McDonalds crew.

I don't see the contradiction. Janitorial duties are at the very worst easy to train any person off the street for. As long as people need any sort of minimum wage to survive you can find a janitor.

But that also means that, because minimum wage, your salary will almost never exceed the value brought to that business. Outside of some super crazy regulations of cleanliness.