Kinda solved with accounts, and/or subs, and monitoring/fraud detection? Or just turn it off for product related searches but keep it on for information related?
Have you seen any large site with user reviews? Amazon? Yelp? Any feedback on a page that matters will be gamed, because anything over what you spent to game it is pure profit. This is not a solved issue in any meaningful way.
Paid users only would probably push it in the right direction. It is unfortunate that the internet has moved into everything is advertising as a business model. I get the appeal but cognitively paying so I can keep my attention seems like a way better model.