I'd suggest that "with chromatic instruments that can handle accidentals, and tunes that mix rhythms and styles" the notion of mode is even more useful. The point of mixing styles is to set up transitions between them, which means having chunks of music in clearly-defined modes, and it helps to understand what those modes are if you're going to compose in them.. The gap-filling development I described is one way of doing that - not so new, the earliest example I gave was from the 13th century.

And you even get it with Highland bagpipe music - as if having only nine notes in a diatonic scale wasn't restriction enough, composers of pipe marches from the early 19th century on went in for pentatonic modes in an unprecedented way. The idea was to liven up the marching by regular changes of tonality. (Earlier Scottish music isn't anywhere near as systematically pentatonic as this Army repertoire - the idea that pentatonic scales are primordial is dead wrong).