I would argue the USGA handicap system is about as good as it gets in determining the skill level of golfer and far better than systems used in other sports ( assuming that the individual player follows the intent and rules of the handicap system, human nature being what it is). Handicap travels reasonably well from course to course, with an assumption that course length remains moderate. For sure, there are some very hard courses by design, but, course rating does enter into the handicap calculation and with repeated play, one can figure out how to play a more difficult course. Golf also provides multiple tee locations making the management of an more difficult course within the grasp of a less skilled golfer.
I'm don't participate in Nastar, but my assumptions are the local course setting is moderate & short and the medal award system is designed to enable participants to medal. It's recreational racing and the system is measurable and objective. I doubt that handicap would carry over the NCAA GS championship I watched with Epic at Stowe this year. Outside of Nastar, is there any system that enables differentiating between skill levels within a group. I've skied with Bob Peters and TetonPowderJunkie an Jackson Hole and would consider both to be level 10 skiers. Both of those persons will tell everyone that at Jackson Hole, they don't consider themselves as top notch skiers. In golf there's a huge difference between a plus 1 and a minus 2
An antidotal story, at this year's Summit Co. Gathering, on the first morning, Uncle Louie asked me how I skied so that he could point me to the correct group, I really did not know how to answer in a meaningful way other than to state I should not be in the top group, but, can hold my own in the second. In golf, I could say I'm a 14.2 handicap. In any case, I've left the golf course, on many times, with a scowl on my face, frustrated with the way I played. I've never had that feeling leaving a ski area, where it's all good. Moral of the story is to smile and enjoy more!