Last year, the CEO of Microsoft Gaming and head of the Xbox, Phil Spencer confirmed that Activision Blizzard video games will not hit the Game Pass until 2024.

Call of Duty Warzone is a free to play game. It's not on GamePass and it doesn't need Xbox Live Gold either. MW2 and its multiplayer component is not free. You need to buy it if you want to play the single player game or MW2 multiplayer.