The issue is there are so many little details that want lighting and shading effects, i.e. trees and blades of grass, that it looks like a glittering mess. The default settings for brightness and gamma washed everything out. Just a bad combination making key details like armies, cities, and roads hard to make out. Reducing the gamma and brightness a couple of notches helped a lot. However, the foliage is still messy. The fix I would love is to be able to use the strategic level icons and map layout to zoom in all the way down to the province level without snapping into 3D view. I really do not have this issue at all with the tactical battles.
Anyway, I honestly do thing my monitor is also partly to blame. Its an older and larger (27") 1080p monitor. So it struggles (I think) to keep up with the quick change across 1,000s of pixels each representing a different detail of lighting, shadows, and texture.