Is FlightAware blocking use of the app now? I assume it's because they've dropped support for iOS 15 (which can be a hassle depending on new APIs they want to use), not the 7 device specifically.
1: I don't see what the big deal is to just put if statements around any iOS16-requiring new features, yet keep targeting iOS15. We did this all the time back when I used to write iOS apps.
It gets increasingly more expensive to support older and older iOS versions. These “new features” you’re talking about wrapping in if statements aren’t here and there. Many upgrades are pervasive, and would eventually make every file a branching mess.
Now, you could argue that that should still be the chosen route. I can empathize with that. I like software that just keeps working forever.