If we're talking interactions with the NPCs, it is obvious that Bannerlord gives you way less tools to work with than Warband, or streamlines them behind menus. I have a problem with the nostalgia-heavy talk of "rich" and "interesting" characters in WB, the game just did a good job hiding the shallowness of the characters.
For reference, I'm a fan of the kind of the storytelling that emerges from CK2, that's the kind of things I find interesting
Bannerlord just gives you way less. It has all of these systems, new and old, and it just leaves it in the game as a half-baked idea that rarely if not ever interacts with other parts of the game, and when it does, it's so shallow a puddle looks a lake beside it.
And no, you just assume its nostalgia talk because you disagree with it, when in fact it is far from it. In comparison to Bannerlord, it's like night and day though. On its [Warband] own, the characters are no award winning characters, certainly, but they were interesting and the way the game mechanics allowed them to interact steadily with the player throughout their progress, called for richer experiences. This simply isn't a thing in Bannerlord, despite all it has ready to start such richer experiences. To deny this and claim that there is no difference in that between the two games, or that WB's lords were just as shallow, is intellectual dishonesty.
I'm sure that Bannerlord could accomplish this. Very easily. The problem is that the developers do not see this, or any of the most famous and desired features of Warband, as something worth pursuing in Bannerlord. Which they readily admit. Their vision is not to recreate everything from Warband, but something I don't even think they know...or are at least willing to be up front about to us.
And I am also a fan of Crusader Kings 2 and its randomized story events, and how you can form enemies/friendships and have events be "remembered" by the world and others within it. It isn't necessarily a very complex mechanic in what it offers, but it's enough to make the game very enjoyable and memorable, and as if your character is leading life the way you desire it. That was something I really hoped would pop in Bannerlord...