It's only a bandaid over a gaping wound, but check out Fakespot, an extension for Firefox and Chrome. It won't help with google play, but when browsing Amazon, BestBuy, or other retailers they use machine learning to detect duplicate/repetitive reviews, and go into reviewers' history to determine if they are trustworthy.
I've seen a lot of "5 star products" get an adjusted rating of <2 because of this extension.