“Old” call of duty is based from WWII, which were made in the early 2000s inspired by Medal of Honor while “New” call of duty is the fictionalized takes within the FPS genre (basically the ones you recognize today). Modern Warfare (the 2007 one) is the title that departed from the WWII genre while World at War tackled at both theaters of WWII (the Pacific and European).
Yep. I think it explains the popularity of HLL, reforger, and the increasing amount of those titles. Keyboard dexterity gets you no where if you can’t think or communicate. Like in real life, the loser is more often outsmarted than anything else.