Reviews are helpful to know if an app you’re buying really does what it says. Sometimes app can overpromise and underdeliver, or sometimes an update to the app can render it useless until a fix comes along, so these are things that new users want to know before they hit that download/purchase button.
However sometimes reviews are spammy or trolling, leading to inaccurate impressions of the app. Previously users could give a review a thumbs down to try and make it as irrelevant as possible, but it looks like recently Google has pushed out an update to its Play Store in which users can no longer give reviews the thumbs down.
As you can see in the screenshot above, users will now only be able to give reviews a thumbs up. Alternatively if you think that a review was done to be spammy, you can also mark it as spam, but presumably these changes are meant to encourage users to give more thumbs up, thus floating more relevant reviews to the top of the list.
That being said, it has been noted by 9to5Google that these changes made are server-side as users are still running the current version of the Play Store, so basically you won’t need to do anything on your end.