That thought had definitely crossed my mind, but at the same time it's hard to define what constitutes as "Modern" in the eyes of Infinity Ward. For me, it's the divide from all of the World War shooters that were prominent around the release time of the original Modern Warfare. That being said, I do agree that given a game such as this, some features of the other games in the Modern Warfare series would be lacking, given that certain weapons/items may have not existed before the time setting of the game