I don't disagree, but I feel like most of the worldbuilding is just the players doing all the work in their own heads. Warband really isn't great for roleplay, people complained about warband the same way back when it released, this was in 2010-11 when big AAA open world games were first taking off, so having an open world RPG-like game, even a low budget game like Warband, without much to do besides combat was jarring for some people.
None of the quests in Warband were really much better than Bannerlord. Most of them were total rubbish fetch quests or the godawful "push these cows to X town". I think the main thing people think of when they talk about Warband being more immersive was just the feasts and campaigns. Even though warband feasts were basically an autism convention, simply meeting the people in your faction in one place was just enough to make them feel like one-dimensional characters and not just zero-dimensional static minibosses. It also drew a distinction in how you interacted with members of your own faction, and everyone else. Similarly it maintained some of the illusion that NPCs had to meet in person to be able to get information.
Similarly the campaigns in Warband were a decentralised group of separate armies who could all break off on their own. You would see in real time who the more aggressive, cowardly or disloyal lords were because they would run away from big armies or rush into battles or just get bored and go home. Plus the player had to actively follow an army rather than the glorified freelancer mod thing they have now.
Just these bare minimum levels of participation gave NPCs a thin veneer of being actual agents independent of the player. Player imagination does the rest. But that just goes to show how aggressively anti-roleplay Bannerlord is that you don't even get this veneer, and instead you get mechanics that destroy this illusion like influence, the transaction menu, perks, clans all acting like a hivemind, factional whatsapp etc etc.
