To be fair, Bannerlord does have some elements of "soul" and personality here and there. A lot of them are concentrated in the early game though, or only visible if you ignore the main gameplay loop to really search for them. The mid-late game is just a split between "constant large scale battle merry-go-round" and "Menulord".
The feeling of a more alive, reactive world which the player can make a personal impact on (in ways that aren't just map painting or crashing the economy) and which communicates the player's actions back to them, full of unique-feeling characters with personalities you can get attached to, and your relationships with those characters affecting the way you play, can be achieved in multiple ways.
Some of the stuff Taleworlds has already said they're working on will help. Turning your companions into nobles could be a nice roleplaying feature that lets you feel like you're rewarding them for loyal service. The party templates thing they announced (with nobles having different recruiting preferences based on their culture and personality traits) will also add a bit of character to each individual noble. Animated cutscenes for events could make the world feel a bit more alive. Claimant quests, if they're anything like Warband's claimant quests, should have somewhat interesting backstories that add to the personality of the faction leaders. Voice acting will add personality to the faction leaders, if they have unique VAs for their greeting lines... although if they just have generic voices, I feel like it will actually make things feel more soulless. Finally, making armor more effective should increase the impact the player, nobles, and their companions, can have on the battlefield. Nobles will actually feel like a bit more of a "boss fight", instead of just another enemy, when you can't just oneshot them; fighting-oriented companions will be more interesting if you can equip them in expensive armor and watch them kill their way across the battlefield for you, rather than just dying in the first few minutes.
As for stuff they haven't announced:
Feasts in Warband made nobles seem more human because you got to see them doing an activity other than fighting. While it's true Warband feasts were visually just people standing in a room, and the only feastly feeling came from the food table and dialogue ("let us raise a toast to our host on this momentous occasion" etc), in Bannerlord the feasts could very easily be made to look more lively and immersive by re-using the tavern animations and the musicians.
Warband's Companions were the biggest source of actual personality in the game. They had unique appearances, specialties, and equipment, and dialogue that covered their life philosophy, backstory, life goals, opinion of groups in the game world, etc and was occasionally funny. During travel, they would tell you stories, bicker with each other (and ask you to decide who was right), or complain if you did certain things their personality made them dislike.
Bannerlord's Wanderers are thinly disguised randomly generated robots who serve only to lead parties or fill party roles, who only speak two lines of backstory to you and then shut up for the rest of their lives (except for mentioning a victory during greeting, or uncommonly objecting to your actions).
TW is opposed to bringing back unique companions, but at least flesh out the random ones. Make more personality traits have objections, make certain personality traits in the party come into conflict with each other with accompanying dialogue, and make companions tell you snippets of lore while travelling. These last two should be pop-ups on the corner of the screen which the player can ignore if they want; ignoring conflicts should result in a small morale hit, and ignoring backstory should have no penalty. This would go a way to making companions feel like true characters with personality again.
Courtship has also lost personality since Warband, as every potential love interest can be "wooed" within an extremely short time and married almost instantly, like buying a car. I'm not saying we need poems, but at least bring back the ability to visit a lady over time to build relations and improve the chances of a successful marriage from Warband, to make it feel more like a relationship.
Lots of other things added character to Warband, like lords challenging you to a duel when you angered them, lords hating you leading to them hiring hitmen to attack you, conversation with the Nervous Man before carrying out his sentence, trading insults with Belligerent Drunks, etc.
They also need to make the Personality Traits system more impactful/functional for both the player and the AI. Some traits just straight up don't do much. Overall, they need to have more impact on the dialogue each lord uses, the tactics they choose (bravery/cowardice), and their political choices (e.g. Greedy clan leaders should vote against castle-building policies, Cowardly nobles should vote for them, Foolhardy nobles should always vote for war, Calculating nobles should only vote for wars the faction has a very good chance of winning). Traits should also have
more impact on which nobles like you and which ones don't.
Relations could also stand a little more work. A common complaint I see is that people don't like that even if you have excellent relations with an enemy commander's clan
and they even say they don't want to fight, if you can't convince them to defect on the spot, then they will always still fight you instead of letting you go. Perhaps with a combination of any 2 of the following - relations above +50, Charm stat above 100, player has Merciful trait- you should have the option of not fighting at all, or at least getting set free if you lose.
Town scenes already have quite a bit of soul and personality in them, and lots of nice little details, but basically no reason to explore around in them because you feel like you're not progressing in the game by doing so. So if TW gave us an optional gameplay reason to explore towns, that would also improve things. Of course, that would be low priority.
The ending (?) of the main quest is another big area for improvement, which could do with more character and dialogue involved. Somehow, work in a way for the main faction leaders (or their replacements if they died) to make an appearance at the end, perhaps before a climactic giant battle or after a surrender (like
victory lines in the Civilization series), and spout some dramatic lines along the "ending an empire" or "preserving the empire" theme of Bannerlord. Something that makes the ending feel more satisfying.