@RainOfPain125 There's a big misunderstanding. Plutonium never said it was giving you the game or DLC files for free, nor that its goal is to provide things for free or support singleplayer?
As a bonus/alternative download Plutonium gives you an option to get MW3 multiplayer files for free including DLC to play on Plutonium. The rest is not Plutonium's problem since it was never mentioned anywhere.
Using DLC files on Steam is straight up piracy and requires tools that can get you VAC banned so obviously Plutonium will never use this and instead removes the Steam check from its games to ensure full control and no VAC ban