Apple is introducing software features to make people think the hardware is progressing. Cell phone hardware has sort of reached a plateau where it is more than capable for us mere humans...so now the excitement is found in silly/ contrived things like "dark mode"...which could have been implemented on literally any cell phone ever made.
If you want "planned obsolescence", look no further! Planned obsolescence came from the auto industry, when each year they claimed great new features, when the new cars were essentially the same. It is tricking people to buy new when the new product is no different from the old one.