What you’re (as you say) missing, is that drones flying long distances can be shot down–but no, not (as you say) instantly. Because they take a long time to travel so far to reach their targets, it’s possible to intercept them (but even then maybe not all of them). How would we stop bombs dropped or missiles fired from planes that take mere seconds to reach their targets? Not possible.
What you’re (as you say) missing, is that drones flying long distances can be shot down–but no, not (as you say) instantly. Because they take a long time to travel so far to reach their targets, it’s possible to intercept them (but even then maybe not all of them). How would we stop bombs dropped or missiles fired from planes that take mere seconds to reach their targets? Not possible.