My iPhone 6S+ is still running super smooth. Maybe because I'm not a huge photography buff or mobile gamer, but each year I wait to see something that will finally make me buy a new one, but each year I just don't see it. I don't know exactly what I'm waiting for, but this wasn't really it. (Also enjoying using one of the last TouchID iPhones during Covid 19)
I hope no one feels 'not needing to upgrade' is a 'bad thing' It's a testament to Apple's build quality and long term support that you don't need to upgrade. Samsung and Android are big on the half baked gimmicks and lackluster supports. Those phones you have to upgrade after a few years as they become more bloated than a Windows 95 machine bought from CompUSA.
Also, I have an Android device and have had them since the TMobile G1. Early models were hampered by RAM scarcity, and each Android release mentioned the smoother UI (it didn't get great until 6.0 or 7.0?). But in general they were OK (apart from a dreadful Samsung tablet I bought) and the only thing that would "bloat" them is running too many apps concurrently (but then they were "freeze dried" until relaunch) or having too many services running, which recent Android has started to kill vehemently like iOS.
I agree with your Apple build quality support though - my MacBook Pro is 8 years old no problems, and I'm happy with the Air 2 I own that is still supported and useful at decent speeds 5+ years after I bought it.