Nonsense.
Software needs to move forward, and it moves forward thanks to powerful hardware to drive new features and increased security. I genuinely believe that nobody at Apple is thinking about planned obsolescence or profits or incentivising people to upgrade; they're only focused on perfecting iOS experience on latest iPhone, but if it can be replicated on older hardware, than great, why not.
A9 was a huge leap forward, and that's why iPhone 6s got three more years of updates than iPhone 6.
A10 was a small improvement, not revolutionary. It still destroyed that year's Snapdragon 821, and iPhone 7 still got two more major OS releases than Google Pixel 1 from the same era. But it's not capable enough for iOS 16.
A12 was another big leap forward, with insanely fast Apple-designed GPU, powerful Neural Engine and much more; iPhone XS already gets more features than X, and will probably get updates for 4-5 more years from this point.
May I remind you that Pixel 3, that came out at the same time, got its last update half a year ago?
May I remind you that most laptops shipped at that time, with Kaby Lake and Zen 1 CPUs, are not allowed to run Windows 11 officially?
May I also remind you that app developers will probably keep supporting iOS 15 for three-four more years from this moment? Which makes iPhone 7 a device that's done its job for 10 years straight. Not a bad run...
These people should chill out.