http://www.ign.com/articles/2012/10/10/treyarch-defends-black-ops-ageing-engine

Maybe the issue isn't specifically with the engine itself but with the same game being made every three months. Perhaps That's what they are actually taking fire for but they are spinning it to sound like it's the engine.

I've lost interest in the whole call of duty war. Not sure why people can't just ignore the game if they don't like it.

If the engine still works, why are they drawing fire?

The age of annual leaps in graphics technology is long gone. If an engine worked well five years ago, chances are that it still works fine today.