I get what you're saying. A lot of the fun from these games is derived from the loot, finding loot, equipping new upgrades, trading loot, etc. I'm not denying that at all. You're throwing the baby out with the bathwater though. In my view the AH didn't do much to hurt Diablo 3, I think that the AH is a good idea in fact. There was an AH in WoW too and it didn't ruin that game at all. Of course in WoW there were other ways to get much better gear such as grouping and raiding so it's a bit different I suppose, although you can't buy the best gear in Diablo 3 through the AH either unless you get extremely lucky. Still the issue with Diablo 3 wasn't the auction house, is was poor build viability and thus diversity along with a retarded itemization system. PoE itemization is much better but it does suffer from the same issues, which is basically that higher numbers in general are the way to go, which is the cause of said MUD-flation. In my view the main difference between the two games is fun things to do, in Diablo 3 there's only one thing to do, level and/or farm, while in PoE you have to do that same thing but you have the addition of fun character builds and the need to remake characters due to the expense of using the same character for several different builds.
In a game like PoE an AH would add a lot, just as it would have added a lot to Diablo 2 and removed a lot of the hassle involved with that game. Let's say you want to make a completely new build, instead of having to find all of the gear for this new build yourself, why wouldn't you want to simply use the AH to trade away the items that you have for the items that you need for your new build? Do you really want to go through the frustrating and time intensive process or either farming a completely new gear set or trading in the game or on the forum?
It seems like you are playing a different game than I am. I've already had two characters doing maps, that's the end-game and that's with minimal trading. There wasn't some huge gear loophole that I had to jump through to start doing maps, I basically just had to level up to that point, that was it. It wasn't hard, I didn't have to farm for a month or even a week. Now if there were a better trading system in the game I wouldn't have to waste hours of my time in the future trying to trade away items that I don't want for items that I do want. All this current trading system is is a huge timesink and a deterrent for players.
The current PoE trading system is akin to what the keying and flagging bullshit was in Everquest. Ok I want to make a new character, let's waste hours and hours of time getting the new character prepared for content that I'm already doing and have been doing. Personally I would be much happier if I could more easily do some quick trading to get my new character prepared and up to the level of my current character.