Application being rejected by nonsense

Well, Apple's acceptance of other apps has no bearing on what happens with your app. They're saying your app is too simple to be an iPhone app. It may be better suited as a web page.

Or an interactive ibook ...

This has happened to me before. Of course, sometimes there's a clear violation of a guideline, whether you agree with the guideline or not. Sometimes it seems like you just had bad luck and got a reviewer who is feeling picky or feels like they want to design your app (I think this may be an even bigger problem with games). Sometimes it seems they have a particular agenda. For example, years ago I used some popular middleware that would collect various feeds into an app, and for a while I had no problem getting them approved. But then they started cracking down on it with the non-enough-functionality citation (Flash is another example of middleware that they didn't want anyone using). The twist here is that this was right after they introduced Apple Maps and the reception was not good, so every time they rejected one of my apps, they said it doesn't have enough functionality, but if you add native iOS functionality like Apple Maps it may pass.

One thing I really don't like is that they have the bureaucratic (and admittedly human) tendency to never admit they're wrong. If I point out a clear mistake the app gets approved without any comment. Otherwise, sometimes they just keep picking on different things as if they really just don't want to approve the app (I recently gave up on a Mac App Store app after the reviewer said it needs a tutorial even though this was just an app update and the app already has on-screen instructions). These days, if it reaches the point I have to appeal to the review board, I just abandon the app. My experience in the worst case is they call me up to say I should redesign the app "from the ground up", and in the best case they insisted I'm wrong but they'll "let it go this time."

The most practical suggestion I can think of is to try adding some native functionality (like my experience with the Apple Maps campaign), especially something they're interested in promoting these days with iOS 11 coming out. Perhaps in-app purchases, subscriptions, text-to-speech...