This is the message I got from them:
We found that the experience your app provides is not sufficiently different from a web browsing experience, as
As of 2018 App Store Review Guidelines:
4.2 Minimum Functionality
Your app should include features, content, and UI that elevate it beyond a repackaged website. If your app is not particularly useful, unique, or “app-like,” it doesn’t belong on the App Store. If your App doesn't provide some sort of lasting entertainment value, or is just plain creepy, it may not be accepted. Apps that are simply a song or movie should be submitted to the iTunes Store. Apps that are simply a book or game guide should be submitted to the iBooks Store.
Assuming:
Apps that are simply a websites should be submitted to the Safari. ;-)