MW2 campaign was a step down from CoD4 campaign, much like World at War's boring Pacific levels were a step down from CoD's earlier world war 2 entries. Its an infantile, childish depiction of warfare that got totally Michael Bay'd and set the tone for what the series would be for the next decade. Plus it ends on a Halo 2 style cliffhanger which is always annoying.
That being said, the 2 or 3 levels where you fight Russians invading America wolverines-style is some of the best spectacle you'll play even in 2020. There's literally a level where you fight in front of the White House, trying to take it back from the Russians trench by trench, room by room. There's the Burger Town siege too, which people have meme'd to death but honestly was a fun level. And the Hans Zimmer score? Incredible.