The enemy AI doesn't know how to bunch their units into cohesive forces, nor lead their big stacks with their family members to build Generals up. I'm getting amazing 10 star generals so easily because I'm rolling over loads of small bands of Gauls led by captains and then the Generals are even leading small stacks wheras the larger stacks are rare and led by captains. If they would figure out how to group their units better it would be much more difficult, and less like I'm fighting a bunch of rabble.