I think it's really good and a huge improvement over Warband. Yes, there is a lot of tweaking that needs to happen, mainly expanding the tasks which can give experience to certain attributes.
First, I don't think people understand how the system work and are just upset it doesn't work as Warband's. You do not get general experience and then disperse that down to skills. You level up based on the amount of Skill Points (SP) you get. You get SP by leveling up certain skills. The xp gain for those skills is determined by certain tasks, denoted at the top where it tells you how to level them up. That xp is then modified by the amount of focus points in the skill and the attribute points in the class. There are also skill caps, which limit the skill points based on focus points and attribute points.
Now you need to do things to get experience for them. You need to buy and sell goods to level up trade. You need to maintain high morale to level up stewardship. You need to use trebuchets to level up engineering. Gone are the days where you 1v100 as a horse archer and use that experience to level up your persuasion. I think this is a change for the better and creates a more immersive game. In Bannerlord, you feel more like a commander and leader than just a gigabuffed soldier who happens to own land.
It seems like many perks, however, are bugged and do not actually work. Hopefully this is resolved quickly so that leveling up has more of an impact.
For those still reading, a bug that you need to start using: When going to the tavern to sell prisoners, do not sell all. Pick the option to choose which you sell, then sell all. You will level up Trade and Rougery doing this.
All in all, great system, just needs a lot of bug fixing and balancing to make the experience better for a player.