What's wrong with Apple's patching?
stopping patching perfectly good working phones is unfair
So how long should they keep supporting them, forever? The iPhone 5S first sold in September 2013, six years ago, is still supported by the latest iOS though it will not get iOS 13.
Not only that, but recently they produced patches for iOS 10 & 11, patching all the way the back to the iPhone 4 released in September 2010, to fix the "GPS rollover" issue that hits all devices using GPS every 19 years.
If they were trying to "obsolete" older devices as some like to claim they would have left that unfixed and allowed the GPS to stop working on those older phones.