A simple star rating isn’t that useful - which is why the majority of platforms that offer customers the chance to review also include text (From Amazon to Google maps to UE Marketplace). Many people leave one or five star reviews that are essentially meaningless and represent uninformed or angry knee jerk reactions to the thing being reviewed. Text gives context to the star rating and allows the shopper to decide whether to trust it or not.
This has been a basic aspect of the internet for so long that surely everyone on the Epic staff is fully aware of it. It must have been planned for Fab and at some point the dev costs or potential moderation costs got in the way - or perhaps things were just running very far behind and there was a desire to launch asap?
Whatever the reason it’s a big step backwards and the developer Qs will also be hugely missed, with this section very often ending up far more useful than the reviews or stars.