I don’t think it’s an issue with the AI, but some scenarios within the campaign only. Certain AIs are much more aggressive than others. Some are defensive, while others attack on sight, and some build armies while others just wait there untill you attack them.
If you’re having trouble with The Holy Man, that’s normal (the game has issues with this map regarding difficulty). If you somehow can’t defeat the Egyptian campaign, then maybe it’s just your lack of practice.