Everyone who says this is the "same" is just trolling or an idiot. Compare the Madden games, which were referenced already. Are they the same every year? Not in the least, other than the fact they're football. Is CoD still a FPS? Sure. But that's the only thing that hasn't changed.
Maps = Different layout, recycled textures
Guns = All the same really, anything that shoots bullets is the same thing, with new sounds (some are recycled) and extremely unrealistic, cheap models.
Killstreaks = I'll give you that one.
Class selection = There's no class selection. There are loadouts, which are based around guns, which are all the same, so no.
Mute functions = Irrelevant.
Madden isn't even an example because in order for them to change anything, the actual sport would have to change, in which case it wouldn't be Madden.
CoD is already unrealistic and fictional and therefore has an infinite amount of space to explore.