The thing is that the CoD community does not want any dreastic changes. Advanced Warfare and BO3 had the new futuristic movements and people thought those games did not feel like CoD. Infinite Warfare went further into the future with wacky new weapons and people hated how it fel more like titanfall than CoD. WW2 changed how the class system works and made it into divisions with certain abilities instead of the class system and the hate got so bad that Slegdehammer had to revamp the whole division system to make it more like older CoD games. If CoD Bo4 feels like Ovrwatch and not like CoD the series will take a big hit. The fanbase likes to have some change but nothing to drastic. If tey had the multiplayer exactly like BO3 but slowed down the advanced movements so it's very similar to older CoDs, and they can add a battle royale mode that does not affect the rest of the multiplayer that would be enough change to make the CoD community happy.
Oh yeah I get what you're coming from, that the fanbase don't like these drastic changes, but what I'm saying is that for me to become interested in Call of Duty again, I personally think they NEED to make these sorts of changes, I mean sure, there's the old saying of "If it's not broke, don't fix it", but after a while, especially with yearly releases... they really need to mix it up somehow, and I don't think removing the singleplayer and adding some sort of battle royale mode is the right mix, lol