Chandelure's hidden ability was never official released in gen 5! I don't know if you were playing another metagame, but Shadow Tag Chandelure was never a thing in OU.As for trapping, I don't consider Arena Trap to be as broken as Shadow Tag. 1st of all you can't trap anything you want like Shadow Tag, and 2nd Duggy as the main Arena Trapper in OU is very very very weak!!! It doesn't ensure OHKOs even with SE Earthquakes (unless it's x4 effective) and it is literally get one shoted by anything, meaning it needs Sash to survive. And with hazzards being dominant I don't think it can easily keep its HP at max.
As for the easy-banning policy, I'm also against it. But this is what most people want, so if I want to play with less clauses it is my problem to find people that want to play with those rules...