Not sure I agree that phone tech has peaked a couple years ago for the average user. What technology peaked years ago?
Camera? Efficient processors? Display panels? Biometrics? Batteries? Cellular/Wi-Fi modems? Emergency satellite connectivity? I cannot think of a single technology (I am on iPhone 14 Pro) that is not at least marginally better than a year or two ago, and pretty meaningful improvement from ~5 years ago.
The rate of technological improvement has slowed or plateaued, but there is a pretty reasonable argument that current flagship technologies are the “peak”, even for average user, if only incrementally. I agree that this plateau, coupled with upgrade cost, is making it a harder choice to decide to upgrade for average user.