The review sites usually will let you check other posts made by the same reviewer. If someone's reviews are all glowing and positive, that may be someone who does their research and stays in very nice places.
To the contrary, someone who has many negative reviews is perhaps more of a whiner or complainer. After all, how many bad places will someone stay at before doing some research?
Also consider the age of the review - is it from 5 years ago or last month?
There has been discussion that RVParkReviews has declined/rejected less-than-pleasant reviews, to the point where I no longer use or recommend that site. (Others will, of course, rush to their defense, for what that's worth.)
I prefer
Trip Advisor for reviews and
AllStays and
RVParky when finding places to stay.
Recently Good Sam Club has started accepting RVer-written reviews, as well:
RVerParkReviews.