Part from the problem was that the low drop chances combinded with easy trading ruined the sensation of looting items which makes it less rewarding.
Many (although not all) people in this particular genre dislike such mechanics.
GGG is fully mindful of this as well as POE Trade introduced the solo-self-found choice to support this band of players disliking the trade option.
WoW trade will not be close to get comparable with PoE trade because WoW makes massive utilization of character/player bound products which Buy POE Orbs PoE won't. Plus, WoW is really a game of any different genre than PoE.
Don't mix MMO with ARPG in terms of trading. This mistake was created once by D3 therefore we all know the actual way it ended.