This, there was a mod (sadly outdated now) on the nexus that changed the AI so they would always priorize border fiefs to siege and it made things SO MUCH BETTER, you knew the armies of both warring factions would be massed alongside the borders so there was also more field battles aswell since they wouldn't miss each other so much by deciding each other to siege the capital deep into enemy territory.
The logic was something like army leaders would priorize taking fiefs closer to their own fiefs to increase their security by adding buffer fiefs between their heartlands and the enemy, it was simple and so effective, a shame the mod hasn't been updated in a long time and no one made a separated version just with the AI change.
Party AI overhaul and Commands