I have never used luminosity masks, because I've never felt the need. Let me explain.
My usual selection method is to do basically what Ansel Adams did in the darkroom. I loosely select an area and feather it. And then capture that selection in a curve. This seems to work 80% of the time. If I need to restrict the tones involved, I can lock down a part of the curve. If I want to dark tones to stay put, I put a point on the curve in that area. You don't want too many points, as you can inadvertently create a flat spot on the curve, which can look terrible.
My worry with luminosity masks is of what I call tonal "constipation", which is basically what a flat spot on a curve does. It crushes tones together. Let's say you're trying to lighten midtones in some rocks. If you do a strong lightening, then any brighter parts of the rocks that weren't in the luminosity mask won't get lighter. But the midtones you worked on will. And the demarcation between the selected and unselected parts my cause some crushing of tones.
I can see luminosity masks working, though, with subtle adjustments, not anything too extreme.