I used to believe them, but recently I realized few were paid ones because they flopped completely and couldn't even reach their project soft cap. But mostly the ratings are genuine, good and helpful somewhat. But don't trust them blindly, as I personally believe blindly following tips, advice in this industry/market will make you fall into trouble.
I agree that any rating can be paid. It all depends on the price and whether this or that agency/website is ready to lose its reputation giving high marks to the frank scam project.