If they want to use an old phone, they can just stop updating their apps and not installing new apps. I still own a iPad 3 with the same, old, software stack from 2013. It still works, I can do things. I just don't expect todays developers to make a herculean effort so that I can run their apps on my old device. It is not just the overhead of supporting multiple different OS versions with different technologies, it i…
The fact that "it still works" isn't the only consideration though - it's the security posture. There's plenty of remotely-exploitable flaws in that software stack from 2013.