The lack of bargaining power in academia exists in part because of the protracted period required to demonstrate productivity. A grad student or postdoc might have invested 3 years in getting a project working only to find that the PI has changed their minds about authorship (for example), or maybe the original idea was simply wrong. This person will now find it difficult to get a different position, and so stays on for a few more years in the hopes of demonstrating productivity, still at the whim of the PI. A Y-combinator funded startup might have gained it's first millionth customer in a third the time and be getting ready to cash-out with an IPO.
In the vein of your comment about Marxism, maybe PIs should be asked these famous questions: "What power have you got? Where did you get it from? In whose interests do you exercise it? To whom are you accountable? And how can we get rid of you?”
I think you also have a problem with gross oversupply. In our industry, you see it in the games programming world. There's just too darned many programmers who think they want to make games, so it doesn't matter how badly they treat the programmers, there's always a line behind anyone who leaves.
It's worse in the sciences, though; a games programmer can go get a different programming job. A slight tweak to the career goals and you go from a realm of gross oversupply to a realm of significant undersupply. What does a highly-specialized organic chemist do?
Per some other comments, the source of the oversupply doesn't much matter to the people in the field.
In the vein of your comment about Marxism, maybe PIs should be asked these famous questions: "What power have you got? Where did you get it from? In whose interests do you exercise it? To whom are you accountable? And how can we get rid of you?”