Bad actors are incentivized without needing direct payments by using fake reviews. They actually put money in because they can get more out. If you start paying for reviews, I would expect this to get worse. While fraud is partially a financial problem, it's really more of a moderation problem, which Amazon does not seem to have the incentive to fix properly. It's also a cat & mouse game.

Bringing cryptos and tokens to the problem is not going to fix this. The best and most helpful reviews are by truly happy customers who need no financial incentive.

You might also look into the sponsored "product reviews" by "content creators" and how they are, more often than not, fluff and praise for money. If you give an honest review for a bad product, you hurt you ability to get future sponsorships.