Just my opinion, but I think this is actually one of the key issues with implementing "pure" learn-by-doing into this style of game (as it stands currently). While something like the elder scrolls has a similar system, it's filled with interesting, linear, early story arcs that make collecting that 1000th piece of iron ore feel less like a chore and more organic. It also has a wide array of earlygame enemies, each with unique weaknesses, strengths, and movesets to keep you engaged as you grind out the levels.
In Bannerlord I feel like I've already done the majority of earlygame quest-types (I know more are incoming, but I'm talking as it is at present) and I'm not sure they even gave any experience? Also there are what, 10 variations (at most) of bandit that you'll continually be farming to level up? And these won't develop or change as you get later into the game, as they would in TES. Given that Bannerlord is an inherently very different game from TES that's pretty much expected, but it makes shoehorning in one aspect of TES that really relies on the rest of the game design pretty jarring to me.
It is a good idea to implement more mechanics to level up and stop the grinding (examples from WB mods: Working in villages, hunting, mining ore or chopping wood etc).
And of course I agree that quests should be more than the basic 10 that we are used to, and of course they should give XP. Also I am a fan of random events that make me choose and get rewards or get in trouble (like in Brytenwalda mod)
But these implementations don't mean that the leveling system must go to the old warband. Why shouldn't bannerlord include those "interesting, linear, early story arcs" like in Elder Scrolls games that you mentioned? Skyrim came out in 2011 I think. We are in 2020. It is possible.




