Reviews also need to be monetised and the best wy is to make sure you are doing them with some profit, like getting paid tips by people. If you monetise by the casinos that are reviewed you would not be able to be independent and the public would loose confidence in them. To get tips and audience you will need to often update the reviews to get good rankings in searches.
You're right, a person who monetizes his work does it with more effort and with more Detail , because he feels that what he does is well Valued, what Happens is that there are very few people who see this work as something worth doing , So there should be some reviewers who have a private service, where they review even each game, or not each game but each type of game, over time it goes deeper, but to be paid they must have a lot of difference in terms of the Reviews that we see, I am a person who always sees and sees very similar criteria from each other, I do not see any difference, the criteria I am looking for I must discover myself with my research.
If a reviewer goes further, that implies that they have to spend More money on the games, and that is understandable, then it is not something that easy, plus the players who have more Experience I know see this as pure gold, because in the end it is It is their money that they deposit in the casino and they want to have the best experience Apart from having the Decent Option for their money to be withdrawn satisfactorily.