Seriously. iOS 15 supports the 6s, released in 2015, and it’ll work fine assuming you put new batteries in it as the battery degrades.

I agree this is important for security updates. However, Android is not monolothic. Browser, carrier services, even the phone app are updated independently of the operating system image for well into the future.

This is ultimately why I switched from android to ios. The new SE at < $200 was also a factor.