I guess people gotta find something to complain about.
In what world does anyone find a 7-year old smartphone still receiving OS support? Outside of iOS, that world is nonexistent. Introduced in 2013, the iPhone 5s received 6 years of feature updates, and just received its most recent security update (iOS 12.4.9) just two weeks ago.
By this time next year, the iPhone 6s will be at the same mark as the iPhone 5s when Apple introduced iOS 13 without support for the 5s. But, Apple has issued 6 security updates to iOS 12 for the iPhone 5s and 6 ever since iOS 13 and 14 came out.
As others have pointed out, cutting off feature updates for certain iPhone models does not render them obsolete. Arguably, the most important updates are the security patches, and Apple has continued to keep that part of the ecosystem current even for devices over 7 years old.
But, a phone won't become obsolete until the apps that YOU use are no longer supported, or the developer decides to no longer make compatible app versions available for devices running older versions of iOS. And that's not something happens overnight. Most developers will typically support an iOS version at least one or two generations past. There might be some functionality missing, but the apps are still available and functional.
Even on our iPad 3, which is stuck on iOS 9.3.6, can still run YouTube and many of the installed apps are still supported even if most of them are no longer updated for iOS 9. But, the web browser does become less functional over time, and several other apps also lost their functionality as the developers moved onto newer versions and cut off support for the older versions. But, again that process wasn't noticeable until about 2 years after iOS 10 came out.
When the iOS 12.4.9 update came out for the iPhone 5s, I pulled my old phone out of mothballs (I bought an iPhone SE 2020 back in May) to install it. About 80 app update notifications also popped up when I fired up the phone for the first time since July (when I installed the iOS 12.4.8 update). For a 7 year old phone, it's obviously still well supported. It's not getting any new iOS features, but the apps still work and receive updates.
I would expect at least the same longevity for the iPhone 6s and any of the newer models after that. The iPhone 6 and 6s were the two best selling iPhone models by volume (with the iPhone 5s not far behind), so I wouldn't expect Apple to jettison that large a user base when a significant part of Apple's business model has shifted towards services.
Remember the times when your father bought a DSLR camera, used it for 10 years, then passed it down to you, and you used it for another 10 years, and then you sold it for quite an ok price at an used items market?
These times are long gone, and so will be humans in the next 50-100 years.
Not that those times ever existed to begin with considering that modern DSLRs only came onto the market just over 20 years ago, and those early generation models are only worth a fraction of what they originally cost. Equivalent film SLRs from that era are currently worth more.