While you can’t remove ratings and reviews on Facebook, you can disable them to prevent them from appearing on your page. This applies to all of your reviews. If you are trying to remove a single review, go here.
To allow or disable ratings and reviews on your Page:
– Click the “Settings” link at the top right of your Page
– Click “Edit Page” in the left side menu
– Next to Reviews, click “Settings”
– Adjust Show Reviews to “Off” and click “Save”
At least this is the current process for turning off reviews and ratings in late 2017. With the frequent changes to Facebook’s settings navigation, it may be a different process by 2018.