This review is for the regular Multiplayer modes only.
This whole game would have been considered unplayable 10 years ago. In its race to please the lowest common denominator, Infinity Ward has created a game devoid of any meaning or structure. Enemies spawn in front of you and behind you simultaneously. There is no front, there are no flanks, and spawn areas are completely unprotected. It's just unstructured chaos.
If it weren't for the racial slurs being broadcast over the voice chat, it would feel like a scripted single player game full of kamikaze bots. After you kill a player, you have 5-10 seconds to move before he respawns and runs back to you to kill you. I could write several pages on all the terrible decisions they made but I'm not going to waste any more time on this game. It's a cartoon that was made for little kids.
PS I've been AFK in a multiplayer game while writing this review. It has been several minutes and the game still hasn't kicked me for being AFK. None of my teammates seem to notice or care.