https://www.polygon.com/2018/9/10/17832952/call-of-duty-black-ops-4-single-player-blackout-multiplayer

Call of Duty: Black Ops 4 is an unusual game. There is no simple elevator pitch to draw people in; the game doesn’t even have a single-player campaign. However, Black Ops 4 developer Treyarch is hoping that doesn’t matter. The studio’s goal is to replace the single-player/multiplayer binary with such a carefully designed variety of modes and ways to play that all fans will be catered to in some form.

That’s a very ambitious goal, and it may make the game hard to market. The team at Treyarch wasn’t even sure its prototypes would ultimately become a Call of Duty game until deciding to turn Black Ops 4 into a love letter to all the things the series does well with multiplayer modes.