Considering how good the hardware is supposed to be, iOS is not that great actually. This is why Androids that have benchmarks score way lower than iPhone can actually feel smoother to use. Apple is brute forcing the thing and making all their customers pay, it's useless to have the most powerful chip if you waste all its power running garbage code.

And this is exactly how macOS and iOS feel nowadays: the hardware is supposed to be great but it doesn't feel that good because the software sucks.