The AI needs to understand how to use certain provinces, like market provinces, more effectively. When you have a market, you need to build the three core revenue generating buildings to get the most out of it. The AI often skips them so instead of a structure giving you anywhere from 600-1500 gold they will have a church or something. I think this is part of the reason I am beating them so easily.
Something else they could do that would help would be to configure their great hall provinces as training centers for governers. By that I mean build the church, law building, and a granary there as they will generate positive traits over time to the governer. Once the governer has leveled up some, the AI could swap them into a market province which generates fewer traits, but gives a lot of bang for your governing skill.