I’m ex-iOS dev so maybe things changed in the last couple years. But Apple was pretty good at keeping old APIs around for a loooong time. Deprecated apis would stay around for quite a while.

New architectures do break old apps once in a while. But even then apps do survive several years without touching. And if someone wants to keep using apps after that… IMO it’s fair to put some burden on user - they have to stick to old OS too.

But if app is subscription, then Even sticking to old OS won’t help…