I think a major problem is how we see the GTS. There are two pages of people asking for Arceus offering Geodudes because obviously no one takes those deals, but also I don't think the people who ask for those pokemon ever take those offers down. I think they make those offers on the game they aren't playing with, their old X or Y game they don't touch now that ORAS is out, just to troll, or thinking if you give it enough time, someone is going to trade them.
Meanwhile reasonable trades go by much quicker, usually when I put up a pokemon on GTS, it's traded in ten minutes. You don't see the many reasonable trades being put up on GTS because they are gone by the time you get their, you just see the ten month old "Zubat for 6IV Arceus" trade that no one is taking, and the owner is never gonna take down, if they are even aware it's still up there. I do believe the vast majority of people who use GTS are reasonable and that 99.5% of the trades on GTS are fair, but the system is set up so that you will always see that .5% of BS.