The problem with Call of Duty is twofold, in my opinion.
1) The game relies on challenge. That's why shooters exist (I'll get to this). The problem is that the game is so badly balanced, it's way too easy. I don't want to imply I'm a pro player by any means, but frankly the game doesn't require much skill over:
- Identify target
- Choose appropriate method/direction of disposal
- Eliminate target
That list might sound expansive, but in practice it's about 2 button clicks (move forward and press trigger to shoot). There's no significant skill; it's just a matter of being able to see things faster and move your fingers. It doesn't help that the selection of weapons are all essentially the same within their respective classes, with minor changes in values, perks that offer no major advantages and have no disadvantages for their use and the majority of killstreak rewards which are completely stupid (you're going to reward kills with more kills?).
It doesn't help that CoD has the Dominant Strategy problem. It's completely possible to win with any weapon, so why bother changing strategy? This makes the game boring, because your patterns are never challenged, and as such there's no point continuing to get better.
2) Games teach skills (see my "What is a game" topic thing). What does Call of Duty teach? Survival skills. The problem is that 90% of the people playing this game probably go to school, work in an office, live at home etc. They're in safe places. They don't need to hunt for food or run from a animal chasing them because they're not primal like our great ancestors. This game is teaching us to do things that are no longer relevant to human life.
The 10% of military personnel who play this game will easily tell you that CoD is NOTHING like real combat. There's no lessons in CoD that can be applied to their active duty. CoD essentially glorifies fighting and makes it seem much easier and more fun than it actually is.