Honestly, my problem with the plot is that WW3 doesn't really feel like WW3. You never get to see a perspective other than Frost's, 141's, & the one SAS operative. Kinda sad, because a game that advertised WW3 should've allowed to play as GIGN forces, GSG 9, Austrian commandos, or more SAS operations at the very least. At least we'd establish that the war is truly worldwide.
New York is fucked for two missions, then apparently Russia pulls out. Why no fighting in the Southern U.S., or anything in the West Coast for that matter, seeing how in MW2, they managed to practically assfuck their way into the East for a good bit? Because I'm thinking Russia, being able to strike at D.C, should've at least hit something interesting in combat.
If Makarov's goal is WW3 on the West, why doesn't he use backpack nuclear bombs or something instead of this long, drawn-out chem warfare fest that seems to end badly for Russian forces? Or what about Makarov's Inner Circle? Why aren't they developed a bit more? Or what Shepherd from MW2's Shadow Company? What's the deal with them in WW3?
Or what about the fact that the world never seems to be in any real danger, despite the fact Russia (along with Makarov's Inner Circle) manage to chemical bomb Europe & assist Russian forces during the invasion? Even COD4 had a sense of urgency around it in a way.
Then comes the ending, which is epic but kinda anti-climatic. Here's a guy, Makarov, who truly wants to bring WW3 to the West, but instead of taking over, say, a Soviet-era nuclear silo & attempting to use that with an ICBM, he apparently decides to hide in an expensive, famous hotel with a massive military contingent of his own peeps & decides to run away when confronted.
Honestly, I may have gotten off-track, but it seems like the writing should've been focused more.