The GV portion of AH is just like the fighter /bomber/attack part of Aces High: you are not going to be good at it until you work with it for a while and begin to understand the mechanics of it. Experience with the GV model teaches you how to aim, lead, where to hit, and a host of other tricks. (If you think 2 months is a lot of time, think about how long it took you to get the flight model down-and that was probably when you were flying 100% of your AH time).
Furthermore, one-hit killls don't just exist in the GV model: pilot kills are a part of the aircraft damage models as well. It just so happens that having a 75mm shell landing in your lap is a bit more traumatic to the human body than a mg round. Knowing where to hit, and actually hitting that place are the key to killing GVs with only one or two rounds.
As for AH being a "flight sim," I don't recall ever reading that HTC was not going to model as much of WW2 combat as possible. In fact, from some of the information out there on what they have said about future plans for the game (infantry/submarines), I expect that althought the CORE of the sim will probably stay in the air, they will not ignore other aspects of WW2 combat.
As it is, I happen to enjoy the GV part of the game. I usually focus on fighters, but running around in the dirt being sneaky can be fun too.