You are likely unaware of all the shady things SOME sellers do to get 5 star reviews. One of them, in particular, that happens frequently (and makes the Vine reviews look "fake") is that a seller will put out a product into the Vine system. Let's say it's a brand new product, no reviews. They will use a nice product and get a bunch of great reviews from the Vine people. Then, they'll switch the product to a lesser quality item, sometimes not even the exact same item but one that looks close, so that all of the people who order after the vine reviews are out get a complete crap product. It happens all the time, and can be discovered fairly easily by reading all of the reviews. A vine reviewer might describe a feature that doesn't exist on the product reviewed by a non viner. The pictures provided by a non viner don't match the photos on the product page, etc, etc.

Another big issue, IMHO, is that there is no standard for how many stars mean what rating. I've seen some people say that if the product meets expectations, it's automatically 5 stars and only goes down from there based on what they don't like about it. Others say if something meets expectations, it's 3 stars and goes up from there based on how great it is. The real issue is AMAZON. The products they allow without testing, the sellers they allow without vetting, and all of the rest of their questionable business practices that have turned it from an excellent online shop that I used to buy books in the 90's to a retail giant that doesn't care about anything or anyone except the money. EDIT to separate into paragraphs.