Remember the first iPhone. No app store, fixed number of first party apps, no wallpaper on home screen (only on lock screen). So I guess some things might have been too "fixed" to be messed with (maybe?)
My beef is, with every larger phone, things should start from the bottom, not the top screen. I mean having the first app on the furthest way from your thumb is just silly. Yes, there's reachability, but that takes extra steps to simply reach that first app on the upper left corner. On my android phone, I only put folders/apps on the bottom half of the screen, leaving the top half for widgets.
And to bring this further, the idea of notification access from the top most screen is also annoying with today's larger phone (this is also true on Android). This is why I prefer Apple's control center (from the bottom) vs stock Android's toggles that have to be invoked form the top most status bar.
I believe an innovative redesign would be a new UI that focus on ease of access from the bottom first.