For the rating data type establish a privacy role called “owner” and set it like this > “this listing’s user is current user”; check all boxes enabling the owner access to everything; uncheck everyone else’s boxes disabling everyone else from accessing/seeing ratings.
Set a privacy rule for the user data type called “own user” and set it like this > “this user is current user” and give it all permissions; for everyone else choose what you want to disclose like first name and anything else that you deem shareable if so.
You will be likely be computing a product’s avg rating as a number field vía flows and showing this result via a text element to any users. With no privacy rule for the product data type there will not be a problem.