In medieval times they had something called an apprentice system. Young adults would accept a pittance for the benefit of learning a trade from the master. This is not the same as indentured servitude.
Apprentice mercantilism is not a bad idea even in these times. An athlete is getting more than just compensation or free tuition. He is gaining invaluable learning from coaches and trainers so he can become Pro material.
I have more compassion or concern for the trainer and water bucket boy enabling the “Star Player” than the athletes in question.
I have a cousin in AA minor league ball. Already has a nice sum in the bank while he learns his trade while striving to make The Show. That isn't an option in the NFL and NBA.