Maybe you've seen or tried one of these "reputation management" or review management companies? At their heart they do one simple thing: encourage positive 5-star reviews and discourage the negative ones. This counterbalances people's tendency to post a review, only when they're upset.
Myself and Anas created a plugin called Starfish Reviews to help people achieve those same results, but without a $300/month expense. And what we're seeing is lots of WordPress webmasters and marketers are reselling it to their clients as an add-on service, for $30-50/month, and still saving their clients a lot of money over the other options out there. Below is an animated example of how it works. Full details here: https://starfishwp.com