You do realize very few of the actual bulk of CoD players keep playing for Campaign, right?
Multiplayer-wise, IW and Sledgehammer's games have been absolute shit since 2011. Which is what everyone else but GAF cares about. Like BO3's campaign wasn't good but that doesn't it stop it from getting 7,000 players on Steam as apposed to IW's sub 2,000, or like how BO3 had maintained several hundred thousands of players on consoles, where IW is barely active in comparison.
Campaign is the most insignificant part about CoD, and that's absolutely proven by it's playerbase. And yeah, going by MP, Treyarch is the only one that makes a good multiplayer mode anymore.