It's not possible to view the overall global reviews and ratings for apps on the App Store. And this is by design.
From the App Store - Ratings, Reviews, and Responses webpage:
Individual ratings inform your app’s summary rating, which is displayed on your product page and in search results. This summary rating is specific to each territory on the App Store and you can reset it when you release a new version of your app.
App Store only shows the ratings and reviews for your set home country (i.e. country your Apple ID is linked to).
And, not only are the ratings and reviews displayed only for the country currently set for your App Store, they can also be reset with the release of a new update for an app. That could possibly explain the lower count of ratings and reviews displayed on the App Store.
The same is true for all the various digital stores that Apple runs (Apple Books Store, iTunes Store etc.).
However, the developer/publisher of app/content can see the ratings and reviews for all the various countries they offer the content.