Similarly to how Reminders was ‘upgraded' at iOS 13 – see Old reminders are gone from macOS 10.14.6
Has there been any further significant compatibility change in iOS 16?

Background: My phone is new, my Mac is old. My main workhorse Mac must remain on Mojave to retain compatibility to a significant amount of pro audio gear which will no longer function in Catalina or newer. I will not be replacing this rig until absolutely forced. An iOS update doesn't qualify as sufficient ‘force'.
If there are show-stopping incompatibilities I will let the phone OS fall behind too.

^{I have no use for Reminders, so this didn't prevent my updating to iOS 13 at the time.}