Earlier quoted context omitted.
I completely disagree. For one thing, a lot of what one learns studying Common Practice music theory most definitely is applicable to modern styles. Things like dominant function, for example, aren't going anywhere. That said, I agree with the point that is implied by your post, namely, that "music theory" as the term is usually used is actually a description of a specific period of music (Common Practice) and it is…
One of the most enlightening things I learned while studying music in college was discovering why classical harmony ended up the way it did. What makes a V7 chord work? Where did augmented 6th chords come from? How did the Neapolitan chord fit into these systems? By looking at the progression of music history from one-voice chants to counterpoint to harmony and then to the explosion of ideas in the Romantic era and b…
1. Studying the history of Western music theory doesn't give you insight into any music, as you claim. It gives you insight into Western music. Check out music from another part of the world with a completely different notion of tuning, different scales, etc, and your music theory background isn't going to help very much. The only thing that is truly universal is the overtone series, because that's based on physics.
2. I think we could come up with plenty of structurally complex music from recent idioms, particularly jazz and jazz-influenced music. I would say that a bigger difference between something like, I dunno, Steely Dan, and Beethoven's Fifth, is length. Popular musicians don't seem to attempt such longer pieces. But for me personally, longer != more powerful. For that matter, more complex != more powerful, but I happen to share your desire for what we're calling "compositional depth", whatever that may be...