And yet some of the biggest changes to iOS happened under his watch.
I'm not trying to be sarcastic here. Can you name a few that you would consider major changes?
Nobody has touched the Springboard in years. App interoperability with the share sheet is really minor.
The Control Center and the "Dashboard" with Extension is far too limited.
Multitasking is way too limited.
I'm really curious what you think.
Apple - in my humble opinion - should first introduce user profiles.
That's easy with Touch ID.
Right now, you cannot hand someone your unlocked phone to make a call or let them try an App or Google.
Then, Apple should "invent" the Home Directory

Yes, I'm serious. A place where I can organise local data that is not copied to App Sandboxes n times when you use them.
Also, Apple should consider adapting more of a classic Desktop paradigm.
Why can't Mail on the Homescreen push away some rows of icons and show 5 mails I can drag and drop on another App Icon?
As long as iOS is so static and "page based" in 2017, it is nearly is useful as it was around 2009 with the iPhone 4.
I ignored the iPhone, 3G and 3GS on purpose.
Mu opinion is that iOS, except for "design philosophy", has not changed at all.
Especially ifg you consider the hardware specs of the recent iPad's.
... and still you can mostly watch Videos with YT, Netflix, or iTunes.
I own many iOS devices, even the 12,9" with a pencil, but without keyboard.
Why? Because I don"t like to type with my hands directly infront of the screen.
But Apple does not like BT pairing ...
No, the iPad especially could be a great device if Apple just would open up.
It's not even about Developer Teams. iOS probably has more teams working on it that the Apple TV (which is iOS), or the Mac.
I'm honestly interested in your thoughts.