I think I see this a little differently than you do, in that I think this speaks to how good Apple is at making its own chips.
If there’s any truth behind the rumors and speculation that Apple will move away from Intel and put its own silicon in Macs as well, then there will be no competition in terms of performance. Apple will leave everyone else in the dust.
You’re definitely right that people aren’t using iOS devices at close to their full potential. It seems like Apple is focusing a lot on AR and machine learning, particularly with many of the new APIs available to developers in iOS 11. It will be interesting to see performance comparisons between the A11 Bionic + Neural Engine on the iPhone X/8 and the A10 Fusion on the iPhone 7 (and A10X Fusion on the iPad Pro) for things like AR which involve a lot of computation.