I'm thinking this too. They need to solve the actual problem, not chase the side effects.
1. They need better AI to determine bad actors. It's not like they don't have smart coders working there (right?) and if you look at a fake user's review profile, it's very easy to see the web of fakes
2. They should strongly consider only allowing verified purchase reviews, or highly devalue or have some kind of moderation for non-verified purchases. ie, you need to provide a unique picture.
3. They should strongly consider permanently banning spammy products that have consistent and high amounts of fake reviews.
Some corners of Amazon's marketplace have definitely started to turn into eBay. They need to prevent that at nearly all costs.
As soon as they accidentally sue one of the people who posted a funny review of their out-of-stock 80 gallon barrel of Astroglide, this will _definitely_ backfire.