You do need to understand not just basic but also some advanced features of C# if I should speak for the current state of Bannerlord modding. The developers don't use only basic stuff, naturally, in the .dll files of Bannerlord that one references for modding. A modder needs to understand OOP first of all, then stuff like generics, annotations, object referencing & pointers and more. So, you do need to grasp C# to a certain degree before daring to make proper mods, I would say.
As I read some of the posts here and in other threads, I realized people are being quite unfair about C# as the modding language. My observation is that they complain about the very abstract and "not easy to learn" features and concepts of C# that junior programmers usually are usually unfamiliar with. For experienced programmers and for those who study fields such as Computer Science, using C# for modding is a bliss compared to that "Python" compiler we used as module system in Warband. It was like a damn assembler
I advice learning C# instead of complaining about its hardness to learn. It is a very popular language and capable of doing many things. Once you know enough of it, you will realize you can do whatever you want with Bannerlord now. I even consider making a voice chat mod after they allow us to host dedicated servers. Imagine trying to make that with Warband module system...