There's a difference between "we'll test and support two color schemes" and "we'll design ui with parametrised colors, shapes and text sizes which can adjust to any change and still be usable". If we settle on bright/dark/colorblind mode selectors that everyone expects to be supported, I'm happy. I've seen themes in the past and there was always a few apps which just can't resize elements in the expected way, or the backgrounds don't tile correctly, or ...