When you double click on a settlement, there is the option to auto-manage the settlement. When this is ticked, the computer will take over the construction, taxes, and recruitment of the settlement.
However, you can also select what the AI will manage. If the auto-manage is selected, they take over taxes, but on the right side of the display, you can select if you want to manage construction, recruitment, or both. And as an added bonus to the AI constructing your buildings, you can have them build economic buildings first by going through the options it gives you. The default setting is balanced, but there's ones such as military, financial, growth, and culture.
I use this extensively. I'm one to focus on conquering lands! Not conquering builders who cannot make the right buildings!
I am the Carthaginian who became an angel, and surrendered his wings for a life on the sea of battle.
My magic screen is constantly bombarded with nubile young things eager to please these old eyes. This truly is a wonderful period in which to exist! - Terikel the Deflowerer