And this is more akin to a situation where someone finds a glitch that allows them to throw someone from across the screen, never having to actually get close and risk attack. At that point, there's two options from the game designers.
They can patch the glitch to restore what people considered the normal, designed, and balanced gameplay, or they can state that's just how the system works now and people need to choose whether to accept that or not and play something else.
Amazon can fix (or attempt to at least) the problem and make it harder for sellers to get 5 star reviews and lower reviews averages for some big selling items, or they can choose to do nothing, and some people will decide to leave and shop elsewhere because they can't trust the site and reviews.
Actually, there's a third option, which is that they can say they are doing everything they can to fix the problem while not doing much, therefore maximizing both reviews/profit as well as customer satisfaction in the short term. If they actually start fixing the problem before too long, it might be the maximal solution for them, but if they take too long their reputation will suffer even more (and it may give competitors a toe-hold). I suspect Amazon is doing this. I have no idea if they can go longer, are at the point they need to change, or are too late, but as a customer it sucks right now.