Major iOS versions are simultanepusly released with new iPhones. Such new iOS versions have higher needs on the hardware, makig them appear somewhat slower. So

Major iOS versions are simultanepusly released with new iPhones. Such new iOS versions have higher needs on the hardware, makig them appear somewhat slower. So yeah this could be seen as planned obsolescence, you still get a major version update on your ‘old’ device for free, with new features as well.