Efficiency of vendor reviews

During planning, how effective have you found these to be? Do you take the information at face value as is written or do you take it with a grain of salt? For those who did get married already, did you write honest reviews afterward to let future couples know what to look out for? Or did you skip over it? Which platforms did you find to be the most accurate for reviews? WW, Thumbtack, GoogleMaps, Yelp, the last two of which don’t allow vendors to remove anything under 5 stars.