Clever AI for me is an AI that behaves believable and smart, but on it's own. In Modern Warfare, or in general the CoD series, the AI itself is incredibly dumb - it does not act on it's own, but much more it's the way they spawn, the way they are positionated and the sheer mass of enemies that kills you. They do for example not follow group tactics, as the AI in FEAR does for example, or make intelligent use of cover. All these things that seem spectacular and smart are hard-coded in MW, the AI isnt doing these things on it own.
There's a reason why there's no map editor for MW: As soon as you'd put a single bot into an empty level, he would not behave much smarter than the A5 template AI does.