D3 AH was a crap idea, terribly implement, that everyone said as much about the second it was announced. Nobody wants that back. But player trading should remain an option. I don't mind if they lock super-high-end loot out from trading so you still need to farm that yourself, but not being able to share gear to help a friend get a leg up on endgame and whatnot is just lame.
The drop problem with D3 wasn't because of the AH, it was because of terrible decisions at Blizzard and bad philosophies. They said as much in a GDC talk about RoS years after it launched, which is why they upped drop rates. They took the wrong lessons from D2 and why people played it for so long.