This is why developers are reluctant to provide visibility into what's going on with development or to release unfinished games, because most players routinely misunderstand the process and how to interpret the state of a game just by playing it.
Now don't get me wrong - the feeling of "what have they been doing for the past decade?" is understandable given that right now Bannerlord is basically just the HD version of Warband with some important features removed/broken, and some new features ranging from interesting to questionable added instead.
But the silver lining is actually hiding in the complaint expressed by this thread's title. The reason modders are able to fix a lot of the issues with the game currently is because Taleworlds has invested heavily in building a foundation that makes that possible. It has taken them a long time to do it, arguably too long, but the moddable engine they have built means that most of the tuning and improvements needed to flesh the game out are accessible to people who were not involved in the programming of the game's engine or core content. That is pure gold, and people are starting to take advantage of it before the official modding tools have even been released. For now the developers are focusing on fixes that modders still can't do, as they should, and the rate at which they've been pumping them out has been impressive.
So go ahead and be upset at the state of the game, there are justifiable reasons to be so. Your expectations about where it should be after so long have not been met. But do not despair over its future potential. As the platform stabilises, content and tuning will flow from developers and modders alike at a pace which might even satisfy players who don't understand how much work it actually takes to make a good game.