I have not used PWP8, but I would be surprised if it was that easy for actual images, where the boundaries of hues are not so clear.
All of these tools do more or less the following: map RGB to some colorspace, do a transformation, map back. The key part is the transformation: the mapping has to be at least continuous (in the mathematical sense), otherwise you get artifacts, yet selective, because you don’t want to affect all colors.
Darktable with parametric and drawn masks lets you build such a transformation in a very flexible way.
In fact, after experimenting with detailed color grading myself, I am warming to color calibration (as opposed to hue shift in color balance rgb). The reason for this is the following: if I have a mask that has a gradual boundary, a hue shift can easily introduce color artifacts when the new color gets mixed with the old one. Color balance rgb handles this much more robustly (technically, because the alpha mixing and the transformation take place in the same space).