The only way D3 would ever in the eyes of the "haters" be considered better than D2, was if it was released at the same time; in the same infancy of the internet community and online gaming and D3 didn't have DRM. If blizzard was to release D2, with better graphics. Change the story and the names of everything, and pictures of the locations to hide the fact it is just D2 over again, I bet you would see as many if not more complaints about it being not "up to snuff" of D2.
I think where this analysis fails is the new players that have never played D2. If you survey these new Diablo players, I have a feeling they also think Diablo 3 is flawed.
I've certainly done my share of thinking about what's different about D3 and D2 and why D3 fails for me, but not D2. Ultimately, when a unique drops, I know that 99% of the time, it's crap. Too many "random" affixes that can spawn and even if RNG is favorable and gives you the ones you want, another RNG will give them low rolls. In D2, there are crappy uniques as well, but when I see a unique hydra bow drop, i know it will be good. Not so in D3.
Certainly the AH has something to do with it. In D2, to a certain extent, everyone is living in their own bubbles. With the AH, that's gone. Every drop on every computer can be placed on the AH. The result is that unless your get very very lucky, your items are worth crap.
I certainly disagree with farming games not being fun anymore. It can be if done right. There's a fine balance of reward to effort ratio that needs to be attained to keep the game fun. Diablo 3 isn't there yet.