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)
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.