Problem with Holo it was hard to follow this concept and create visually distinct apps. They would all be cold white and blue. Material design gives for more variability.

Some apps did change the accent color, but it was very non-trivial. Material design comes with tintable controls out of the box.

There were two Holo themes: dark and light. You'd pick one and extend it with the style of your brand. My only gripe with it was that there's no built-in mechanism to add shadows to things — you have to use pre-rendered shadows as bitmaps or generate them on the fly.

Anyway, "dark mode" is totally doable with Holo.