That is a good comment--you need to understand the music that you are playing and how it works--as a folk musician, you are your own arranger, so the better you understand what has been done and what is possible, the more interesting you can make your music--

As to other stuff--my big complaint was that there were a lot of simple things that I needed to understand about music and my instrument that no one ever told me, because they were busy either dispensing a standard academic lecture on classical music theory, or a very idiosyncratic discourse on something that they happened to really like--

As a musician, you are confronted by your limitations every day--if you understand the basic theory of what you are doing, it lays the foundation for you to move ahead--but it is easy to get buried by all the non-essential but important sounding stuff, and get so confused that you just stay put!!