Every moral system I can think of would prescribe that, everything else being equal, you should attempt to change the behavior of the company you find unethical

Every moral system I can think of would prescribe that, everything else being equal, you should attempt to change the behavior of the company you find unethical while you have at least some power over it, rather than removing yourself from a position of power to affect more ethical behavior. It strikes me as very strange to advocate that folks remove themselves from positions of power to effect moral progress.