It's a cool game when I want to just smash armies together and eat territory but I would be willing to bet a lot of money that no one - not even the devs - have played this game to 100% completion. This is a very very long game. It takes forever to get everything done. Perhaps thousands of hours to finish one full game.
This is coming from someone that has completed many Civilization V games. They're much shorter.

It's an army battle simulator with very little script. The borders will always soon look very different from how they started. There are so many other entities on the map roaming around (hundreds? thousands?) that it's fairly impossible to brute force things for long. As soon as you start pushing a huge force in one direction the tiny enemy forces take everything behind you again because they're faster. So you basically have to do everything slowly and calculated or you lose everything you spent time and effort taking as soon as you leave it undefended anyway. Everywhere is crawling with vultures.

• It feels so satisfying to smash things in battle. Whether I'm slapping something in the face with a giant ax, running over a straggler with a horse, or landing a javelin in my opponent. And with the dance of directional blocking and attacking it's easy to be drawn into a fight with one enemy and lose awareness of other aspects of battle. It's too complicated to treat as hack-and-slash.
  
• I love that every faction has a general inspiration from the ancient real world (Slavic, Mongols, Romans, Celtics, etc), and they're all unique with special army units. Khuzait for instance - inspired by the Mongols - has army units focused largely around horse archers and their home area is open desert. Every faction feels different to fight as or against.

• Bandit hideouts are especially slow and dull. They're the one thing that desperately does need a "send troops" option. In the early game you can use these missions to train up your ranged weapons, but they're completely uninteresting wastes of time when you're mid/late game.
  
• The "Roguery" tree is useless. There are a lot of individual perks throughout the sheets that aren't useful but that entire perk tree is standout as useless.
  It kind of reminds me of the uselessness of the speech tree in Skyrim. But there's actually a speech tree (called "Charm") in Bannerlord that's actually generally alright.
  
• I don't like the way betting works in tournaments. There shouldn't be a limit to what I can bet in general, but if the limit is so small I could make more (faster) just by selling a stack of salt then the tournament doesn't feel very rewarding. Why am I putting down 600 denars to win 850 denars? I'd only be winning a difference of 250 denars while risking 600!
  That's trash! I'd get more from a random battle - plus loot. The idea that winning a tournament with maxed-out betting isn't even enough to pay a single day of rent in this game is a problem. I should be able to set myself up for at least a week at low level if going through the multiple rounds of a tournament or what's really even the point?