It really doesn't matter if there are some of the fake bad reviews by the frustrated gamblers or sometimes deliberately forced negative reviews by other competitive casinos. In both cases, they can be easily overlooked if the casino itself is good and the genuine players are happy there as they will oppose those reviews, or there would be many better statements from them about the casinos.
But having some bad reviews on a gambling casino still damages its image. It makes new users to be skeptic to try that gambling website. Genuine users will oppose but as a new user you will definitely have doubts if you read some negative reviews.
However, if the casino does not have a good reputation, then 90% of the reviews about them will be negative and people like us will avoid those casinos after seeing those reviews.
There are some bad casinos that pay some people to make good reviews about their platform. I see some of those website having good reviews but when I try them, the reality says the otherwise. Even checking this forum, they've been said that new users should be wary on playing on their website.
Best thing to do is firsthand customer experience to know what is really true. There are even instances sometimes that the experience from other user doesn't occur to your side and you can play without any hassle.