I wonder how many "genres" of classical have either been lost because time smooths over the differentiators. We may, as a society, reach the point where ABBA and NIN are just lumped into the same genre.
You're probably correct..."oh right, that music that started in the late 20th century with drums, bass, guitar, keyboards and vocals."
Who knows if, 200 years from now, reggae will be regarded as a different genre of music, or put in there with ABBA and NIN? But we do have one advantage over classical composers: we have recordings of the music. People still debate whether Bach intended much of his music to have swing, and that it wasn't as metronomic as people think. The theory is that it was something kind of understood, so there was no need to notate it. Maybe there was a sub-genre of composers who preferred a more metronomic approach, while others didn't. We'll never know. Even I
wasn't alive back then.
Taxonomies evolve from atomically granular to rationally generalized over time. We are somewhere in between...at a stage where almost any new thing can be defined with a compound term: Synthwave, Triphop, Pirate Metal, etc.
Pirate metal is a new one on me...! Arrrr-TWANG!