Bannerlord takes Mount and Blade Warband to the next level. More interactive combat, lots of quality of life improvements, and a more structured Calradia. Do you like being the leader of armies? Now you can do that without grinding relations and hoping for the chance to become the marshal of the realm.

Some of the great things of Bannerlord include the combat improvements, the AI improvements, the ability to use true strategy to win battles like a medieval genius, and the ability to have clan that can raise children, have direct relations with other clans and can own fiefs.

For the Warband players: Here are some of the negative changes from warband that I'd personally like to see fixed...
1) feasts no longer exist, while not an important mechanic, it still helped make the world feel more alive and immersive.
2) clans are strict, if their leader says no, that's that. I think this is a big problem, as you can make the son of a lord your best friend, when you make a kingdom, that man will never join until their father agrees. It very much feels like a "Can't man, my dad said no" type situation. They also don't have the relations based orders you can give to parties such as "go attack this village" or "target this castle, it's weak" that could be helpful to strategize enemy movements.
3) You need to have a clan rank to start a faction, and you cannot be a mercenary while you have land. While I don't think that being a king should be as simple as the owning land, it shouldn't need to take hours and hours of grinding renown being stuck in a limbo.
4) Only castles and Towns are obtainable fiefs, no longer can you donate worthless villages to people to please them, as all bound villages to a castle or town belong to the owner of the town or castle. Don't expect to be given land when you join a kingdom, first the land must be taken and the lords must be willing to put you into a vote, and then you still need to have enough influence to successfully surpass the others to get the fief. There is no monetary compensation or ability to rebel if a fief you take over is taken by someone else in a vote, it's more of a tough luck maybe you can get the next one.
5) Claimants are no longer a thing anymore, still wish they were, at least for the non empire factions.

Finally, if there's anything I want more in this game, it's kingdom diplomacy, it doesn't need to be crusader kings or anything like that, but literally anything that could be like factions that want peace in times of war, or the ability to sway opinions of your enemies to try to get peace, or the opposite and try to declare war. Delegation gifts to improve kingdom relations would be great, and maybe even that if two kings are friends, they won't just go to war randomly.