When you list a product on Amazon, you have to pay 10-20 of those Amazon Employees to review the product at arms length.
Say each reviewer is given 2 hours for each product, before you can list a product on Amazon you have to pay $2 x 20 x hourly rate.
These should be the only reviews.
Or you can sell your product with no reviews.
But also, you don't want people to be too close to a range of products so they can be somewhat objective. For example is swimming shampoo a real thing? or is it just normal shampoo that costs more?
Here is Australia there is a range of over the counter pain killers, all the same brand, all with the same active ingredients, but marketed at different kinds of pain, and at different price points.
https://www.amazon.com/gp/vine/help https://www.amazon.com/gp/help/customer/display.html?nodeId=...
It's essentially an ad, not a review.
My impression is: you pay, you get 5 stars. They buy a product themselves and didn't like it, you get 1 star.
Maybe it's just not an issue for most people because they don't know that reviews could be bought, so any and all reviews are great for making the sale from Amazon's perspective. If the minority that chooses to shop elsewhere grows too large, they can always make a dramatic gesture, punish a dozen people with fake reviews and donate to a children's hospital.
Simply limit "review rights" to users who have made a certain amount of purchases, are already subscribed for a certain amount of time, etc.
And the people who answer one of the questions with "I don't know", too. Why did they bother typing anything at all?
My theory is that some people can't imagine that people aren't talking specifically to them. You see them in chat rooms answering every question as if it was posed them to directly, even when it was obviously directed at someone else.
Maybe reviews should be limited only to certified buyers or only those should be added to stars /rank.
If you want to test longevity Amazon could track warranty repair / replacement claims.