One of the deepest issues I see with music theory as it stands is simply that harmony is "overworked". It has a lot of baggage that is of some use conversationa

One of the deepest issues I see with music theory as it stands is simply that harmony is "overworked". It has a lot of baggage that is of some use conversationally to discuss different eras and genres and to play polyphonically, but also not really needed to write interesting music or make sense of an existing piece. Most harmonic structure can be described very well just in terms of scale degree emphasis, and overlapping scales where the structure is complex. And it's quite easy to stumble into "spicy" yet listenable results by setting yourself up with two scales, playing monophonic arpeggiations that interchange them, and then condensing those into chord progressions. It's much harder to reach those chords by starting with a list of block chords, because that medium works in one scale at a time, so the notation quickly gets unwieldy.