Lobster, as people here have pointed out repeatedly, actively using and relying on the call screen during a call is common for many of us using earphones or the speakerphone mode - especially if we are managing a conference call for work. So we are not all pressing our phones against our heads on calls. Many of us are also simply more comfortable having the RF transmitter in our phones at arms length from our brains during calls anyway. For me personally, I have trouble actually reading display text on the gray background, aesthetic considerations aside. That's a functional accessibility issue. Dark Mode should mean Dark Mode.
As for button repositioning - people will put up with interface changes which provide utility without taking too much away. But swapping existing button positions around on such a vital and memorized screen is akin to putting the digits of the keypad in different order. It’s as if the 9 and 7 keys had been swapped for no apparent reason. Sure the 9 is still there, but why create the cognitive burden of learning a new position for it?
Aside from the accessibility issues with the gray call screen, most troubling for me is the End Call button now being crowded together with the others. I’m afraid to have my thumb anywhere near the button cluster during an important business call now. It used to be safely separated from the main cluster at the bottom of the display. That was functional genius - every little detail went into that original call screen design and it was completely thought through. If any of the original iOS designers ever read this, I would like to thank them from the bottom of my heart for providing us with such functional design excellence for so many years. I can still look at the iOS4 call screen from some 15 years ago and feel right at home with it. Now I'm just lost in disbelief over needless change.
We are not Luddites here resistant to any change at all. We just need to have back what worked so well for so long. That’s all.