my tinfoil-hat theory is that on each OS iteration Apple adds a new feature that leverages the latest chips hardware acceleration features and for older chips they do software-only implementations.
they ship-of-thesseus the crap out of their OS but replacing with parts that need these new hardware features that run slow on older chips due to software-only implementations.
I got the first generation iPad Pro, which is e-waste now, but I use it as a screen for my CCTV, it cannot even display the virtual keyboard without stuttering like crazy, it lags switching apps, there's a delay for everything, this thing was smooth as butter on release.
they ship-of-thesseus the crap out of their OS but replacing with parts that need these new hardware features that run slow on older chips due to software-only implementations.
I got the first generation iPad Pro, which is e-waste now, but I use it as a screen for my CCTV, it cannot even display the virtual keyboard without stuttering like crazy, it lags switching apps, there's a delay for everything, this thing was smooth as butter on release.