I thought the same thing, so I disabled f.lux and turned on Nightshift on Mac OS. To my surprise, nothing happened. It turns out that it doesn't work with my monitors for some reason. They are non-Apple and thus not supported. Back to f.lux which works perfectly. Additionally, f.lux has more con-figurability, it's easy to disable quickly if I need to for a short period, etc.

I personally prefer the OS doing less, but more stability and better, and allowing me to customize through apps. I feel that over the last few years, Mac OS has gone "wide" with features and has gotten less stable.