If ground combat only rotated between ten different map+ alien combinations, would you play it? It would become tedious with an optimal solution for all the ten setups. The game would be solved sufficiently in hours. Ground combat has inherent variability to it because the setups are different. In air combat, they are not.
In your following point you emphasize detection and range. Those are geoscape-level air combat attributes. Making the actual fight between aircraft more or less automatic as it is in UFO defense does not remove those, in fact it emphasizes them. From my point of view, the geoscape part of air combat is the actually interesting part, the actual combat itself becomes quickly solvable.
As to your snobby sentence everyone is referencing: in general, thinking of a game design system is not so hard. Implementing it is not nearly as hard as it seems so long as you're willing to completely cut graphics and other such things required to make it marketable. Making it work well with every other system is damn near impossible and the reason both of us haven't made a game. Unless of course you just copy an old game. So you're not entirely wrong. But mostly.