I haven’t upgraded since 2020 and I still don’t have a good reason to. My iPhone 12 still runs great. I use a real camera for photography. Other than the cameras, what has meaningfully improved over the last 6 years?

Yea I just swapped my jogging/beach iPhone from an Xr to an iPhone 12 and wow, it's so much better than the Xr and pretty much as good as my "proper" phone, an 17Pro. It's got 4G RAM instead of 12G but it performs almost as well. Xr->12 is a huge leap in performance and I noticed it straight away. But the 12 against the 17 is much harder to see the difference. Less redraw of icons on the main screen is the primary thing I've noticed.