The one thing I regret is that my piano teacher of seven years, while a concert pianist of some reknown, taught me nothing about music theory or anything besides classical music. It wasn't
fun. I stuck with it for a while but eventually quit when I felt things were just stagnating.
I can play music on the guitar, now, that I have no idea how to manage on the piano.
OTOH, I can't do Beethoven on the guitar.
(edit) I'm sure that all sounded like I know music, but I'm not 1/16th the musician nostatic is. Actually, I'm not 1/64th.