The thing people need to remind themselves is that - it's subjective. You don't really know how good a product is, unless it's in your hands or you've got hands-on experience. It sucks, because we can't demo everything and it forces us to sometimes take financial risks.
It just comes down to what you're looking for out of a product. Is it X-free from Y chemicals? Does it meet a specific standard you're looking for?
What pisses me off with reviews sometimes is how vague and scarce a review can be. Most of the time it's people just going "It works! Thanks!" or "It sucks. Don't buy!". Like, I can't evaluate a product on that alone, I need a little more to work with. And a lot of the time too is that people will just complain in a review of something that isn't even about the product like "it didn't arrive on time...0 stars". How is that relevant to the product? Sounds more like a problem with the shipping service, two different things.
You don't need to always write reviews spanning 10 paragraphs. But christ, just write more than "it sucks, don't buy". Why does it suck? What makes it suck? Come on, details.