Perhaps you should do some research before regurgitating things you've heard..
Bear in mind this phone will be five years old this year. The fact that it's still receiving updates is one thing, and the fact that these updates are actually speeding up the device makes it even more remarkable.
Are you referring to just the latest update ? Cause historically speaking, from experience the last update available on a device is a maior performance step backwards to the OS that shipped with the device. If it was not plannned obselenece , why can not install an older IOS like I can on a mac?