Honestly i had envisioned this situation before they wen live.
A random low-level GR with an incomplete/bad designed build is crap. Anyone can clear it, no thinking required, and rewards are pretty MEH. Competition wise, they suck because clears are so fast and anyone can luck their clear out.
Challenge rifts should be about a 55-65 clear with a thought out build. It doesn't need to be higher so you have a lot more leeway into building, plus it represents a decent entertainment since the run isn't done in 2 minutes. Also, builds should be validated fisrt to avoid stuff like the NA/KR LoN with no ancients build crap.
There are a lot of fun builds possible in game that just get rekt because GR simply suck ass as endgame promoting the "one and only" mentality for each class. There are synergies working that aren't played just because some others deal 10x damage. While these builds are not feasible for Ladders and GR pushing, they're still a nice change from meta and deserve more visibility.