Maybe in a larger sense Yelp is working. The people paying for the rooms are unhappy with them. They leave negative reviews. Perhaps the next wedding couple do

Maybe in a larger sense Yelp is working. The people paying for the rooms are unhappy with them. They leave negative reviews. Perhaps the next wedding couple doesn't dig into the reviews and just skips over that place in favor of somewhere the guests will enjoy more. So the reviewers end up benefiting future would-be-customers, albeit indirectly. If the hotel doesn't like this dynamic they can simply refuse to book wedding parties.