I feel that quote more likely is pointed at "music appreciation" as a written work, versus understanding the theory. I know a few musicians who are happy to use terminology from theory, "I love to write songs with diminished and sustained chords".

This seems like a great resource to me, a classically trained pianist who is now playing different types of music.

There are several music samples in there...

Example: https://musictheory.pugetsound.edu/mt21c/DiatonicChordsInMaj...

skill issue.