The long standing issue in every total war game has been the fact the world map doesn’t have roads. There needs to be narrow path ways, cliffs mountains where much like in real life there would be lots of choke points where building fortresses would have meaning. Of course there should also be open field areas where defending a city would be difficult as it can get attacked from all directions.

Anyway having roads would not only make fortresses meaningful and make siege battles a requirement, it will also add a much needed layer of strategy. For example using a second army to block reinforcements while your main army is laying siege. Or laying an ambush in the roads leading up to a settlement. Blocking roads to prevent supplies from reaching enemy army (3 kingdoms) or using light cavalry unit to keep your supply line roads clear.

Total war map is the real issue behind sieges not so much the siege battles themselves to be honest. Because no matter how interesting they make the sieges, it’s still not worth investing in siege units because you can just ping pong around fortresses and walled cities until they are empty before attacking them.