GTS has always been iffy. Expecting anyone to follow through of what you've asked and what they're presenting, is very much wishful thinking. It's best just to follow what Peitharchia has said and just go to message boards. Your chances increase exponentially if you do that.
I don't need to use the GTS for much anymore since I've completed the National Dex a while back; occasionally if I want a hidden ability I might go to GTS on a whim. But, I would love for GameFreak to implement the stats/ability/nature/moveset available for showing of the Pokemon someone has put up for offer. It won't prevent people from doing the usual GTS "Weedle for Zekrom" mentality, but it does help out in that you can now spot out who's telling a fib when they say "6IV Adamant + Egg Moves" as a description.
Here is an amusing story for GTS though. Back when X/Y came out and PokeBank wasn't available, there were a bunch of people putting up their Mewtwo, Yvetal, Xerneas, and Zygarde up for trade, asking for Ratattas and other unobtainable Pokemon, pre-Bank. Since the Japanese were the first ones to have access to PokeBank (for that short stint before the server got slammed), some players were snatching up Legendaries left to right, lol.