Yeah, the TMP admirals' uniform is superb too, for similar reasons. Simple, elegant, clean lines. No surprise it was basically reused in the new films.
The rest of the costumes in TMP are much maligned, the one-piece outfits especially, but I've always felt they were pretty coherent designs. I think if you made the pants black and used slightly less pastels, you'd have some very timeless costumes.
They seemed bland to me, so I guess I agree with you there. Maybe utilizing the Original Series color scheme - black pants, department color shirts (with black collar), would have improved them. Kirk's admiral uniform did look kind of nice in contrast, and the updated look in Into Darkness looked nice. The formal uniforms vs the ship uniform contrast was interesting to see in the new movie.