Well I use it on my personal site: the colors change with the weather and seasons [1]. Oklab’s so-what is that the hues are perceptually a uniform brightness, unlike HSL (which I started with) where blues and reds look a lot brighter than greens and yellows at the same saturation/lightness.
So in my case where color shifting is happening, Oklab actually helps. I don’t know how it’s better than HSL for simple UI elements unless maybe you can get physically brighter values that pop out more on certain screens.