I agree with the sentiment that the mere existence of retail and hospitality billionaires is unethical: Jeff Bezos, Elon Musk, the Waltons. Their wealth accrued/leveraged off unpaid wages.
What about musicians, athletes, entertainment creators? Jay-Z, Paul McCartney, Michael Jordan, Steven Spielberg, George Lucas, Oprah?
I don't have developed thoughts on this: if you create a billion-dollar brand from the ground up, is that still inherently unethical? I don't have a “why” for that line of thought, in either direction.