The toxicity of the current setup cannot be understated. A $3 million advance on one book to one author is 300 $10,000 advances on 300 books to 300 authors.
My opinion is that they need to stop paying advances to established authors and celebrities anyway, and move to just paying on a royalty-based model for them. They don't need the money, it would balance the books better at the publishing house and it would be fairer if publishers could put that money into new and emerging authors (I have seen first-hand how arbitrary the decision-making in publishing is).
I don't like advances as a system, it feels too much like borrowing money on the promise that I might be able to repay it one day. Only if you default on it through no fault of your own, your career is over rather than facing any legal action. And the success of the book is almost entirely down to the marketing campaign and not all books are marketed equally (not even slightly). I had an argument with my publisher once because I refused an advance on these grounds. They just couldn't fathom it.
There is no way a movie star or a celebrity needs $3 million more than Karen Smith the unknown author who has borrowed on credit cards to get her breakthrough novel professionally edited so she stands a chance of getting her first contract in the modern publishing landscape.
It was extremely unlikely that book by that author was ever going to recoup a $3m advance so I have to wonder in these sorts of cases whether the publishers' commissioning editors are getting a cut from the celebrity authors. Nothing would surprise me in the publishing world TBH, it looks like an amazing institution from the outside but it's really quite corrupt and morally bankrupt in key places.