I completely agree... and yet there is one prominent counterexample: Wikipedia. When Wikipedia came out I was absolutely certain it would not work. And yet, somehow, it does. There are trolls, and controversial pages have to be locked down, but overall the site does astonishingly well. It's the go-to source for general information on the Internet, at least as good (and in many ways better) than expensive curated sources.
I don't completely understand what it is that makes Wikipedia work. I'm sure it's a lot of things, and at least some of the things also contribute to dysfunction (like deletionist moderators). I don't know if that can be adapted to review sites, which are at core about opinion, while Wikipedia's guiding principle of objectivity gives it a touchstone that all non-trolls more or less agree on.
The trolls don't, of course, but somehow the fact that the non-trolls outnumber the trolls makes them relatively easy to spot and manage, though there are still problems. Especially in out-of-the-way places, which is the other difficulty with review: most places will get relatively few reviews and won't have millions of eyeballs on the lookout for trolling.
Still... the reason I brought this up is that somehow, Wikipedia works, and I would have sworn it wouldn't. So maybe, just maybe, there's some hope for review sites as collaborations. It won't be as simple as reverting the many different kinds of bad reviews (from outright trolling to "I hate spicy food so you shouldn't go to this Mexican restaurant"), but I'm uncharacteristically optimistic that there might be a route forward. (I'm certain, though, that Yelp hasn't found it.)