Look at COD4. Simple, straightforward, and made sense from a gaming perspective.
I didn't play WaW, but look at MW2. All of a sudden visibility turned to sh!t because the designers wanted to give the illusion of a hazy environment, and a rainy environment, and a snowy environment. They made intricate maps, with all sorts of d0uche everywhere for the d0uches to go.
They made camoflauges that matched the environment, and now we have things like rockets that fck up the feeling of the map no matter where you are, we have zip lines and bridges that break away.
Are you fcking kidding me?
None of these things are necessary and none of them facilitate game play. They are exhibitions of what designers can do with graphics and player-environment interactions. It's a d1ck measuring contest for the graphics department, and what people who play the game want, falls to the wayside because what we want, and what we need isn't going to land anybody any big time contracts anywhere.
So, I think that map design sucks so bad because it's no longer about the players, or about the game. it's about the designers.