My iphone6 would still be working but I did something not so smart. When I went to the gym daily I locked my wallet and iPhone in my car glove compartment then went to workout. Over time the iPhone battery got screwed up when the phone got cooked in my car oven.I had an iPhone 8 that was replaced with an iPhone 12 Pro Max two (or maybe three…? ) Christmases ago.
The 2 major differences I noticed were a much better camera, and much longer battery life, even from when my 8 was new.