I'm a multiplayer cod type of guy and the way to unlock guns was a new experience which I can't lie was quite enjoyable because it forced people to explore around different type of guns, the maps were well detailed but there is mostly one complaint which is the camos, it was WAY too easy to get a camo like diamond making it feel not as special when you unlock it since everyone else already has it from how easy it is, and if diamond was easy don't even get me started on gold. The weapon levels were waaaay to low (level 20)
If you want an active multiplayer cod i'd suggest Black Ops Cold War, it brings back old maps, it makes your gold and diamond camos feel rewarding and there is much more to achieve as the guns go to about level 60+ giving you more of a variety of attachment options.