You've said what I've been trying to articulate for a long time - in much better terms than I ever could. Thank you!

I like the dichotomy of songwriter vs. producer - but I would guess it isn't always so discrete - i.e., production and mastering is essential to conveying the emotions and moods of the songwriting. In fact, I would argue the lyrics are often overemphasized in analysis - they are more of a vessel for tones and cadence of the song.