To me, it's subjective. What one person considers to be dumbing down, another considers to be streamlined.
You might say for example that denying is useless and removing it has streamlined the mechanics, but others say that it adds depth and challenge to the gameplay, and removing it would dumb down the game. Both are valid points and correct in their own way.
Another example would be the new Xcom game, Enemy Unknown, and it's removal of managing ammo. Some say it's taking away from the complexity, but others say it was a useless feature to begin with. (I would tend to agree with the latter, and the fact that you still have to manage reloading your weapons is evidence enough that it's not dumbed down).
You might say for example that denying is useless and removing it has streamlined the mechanics, but others say that it adds depth and challenge to the gameplay, and removing it would dumb down the game. Both are valid points and correct in their own way.
Another example would be the new Xcom game, Enemy Unknown, and it's removal of managing ammo. Some say it's taking away from the complexity, but others say it was a useless feature to begin with. (I would tend to agree with the latter, and the fact that you still have to manage reloading your weapons is evidence enough that it's not dumbed down).