Thats true, i wish you could choose between sieges and battlefield.It's a lot of fun but it's not perfect. I tried Chaos yesterday and in forty turns I had two battles. The rest were sieges which I auto resolve because they're so boring.
Empire campaign is better but also annoying since you have to run all over the map putting out fires after they nerfed garrisons so cities fall way too easily. Even high level Altdorf is an easy auto resolve for the ai now.