It doesn't matter whether D3 is an MMO or not. It's a pointless argument. A red herring.
Let's recap:
DioWallachia said that D3 developers could have learned a lot from "other games".
Ruzinus asked, "What kinds of other games?"
DioWallachi suggested D3 devs ought to have learned from failed MMOs.
It doesn't matter whether or not D3 is an MMO or not in order to have learned from one (or several) of them. Personally I wouldn't consider it an MMO, since 4-player co-op doesn't strike me as "massively multiplayer", but in the end it's all beside the point. The point is that DioWallachi has suggested a place that D3 developers could have learned something, but hasn't suggested anything specific that they ought to have learned.
Also, that information about D3 being an MMO early in its development? Pretty sure that was back before everyone who had worked on the earlier Diablo games left Blizzard 10 years ago. The current version of D3, which has been in development for the past 6 years, was never intended to be an MMO.
DioWallachia said:
...you killed me with these sentence: "IT IS PURPOSELY A LESSER SKINNER BOX!". Can i ask what they were smoking? i could understand if they fucked up by sheer incompetence but PURPOSELY?
You clearly have no clue what Ruzinus means by "Skinner box". A Skinner box is a BAD THING FOR A GAME TO BE. It is a cheap, superficial way of hooking players based on compulsion INSTEAD of fun. Ruzinus is arguing that D3 tried to be less of a "Skinner Box" and more of a fun game. It's similar to arguing that he wants McDonald's fries to actually taste good, not just to be hooked on them because they lace the cooking grease with heroin.
Go re-read all of Ruzinus' posts and mentally replace "Skinner box" with "bad game that uses cheap psychological tricks to addict me".
Now, on to the main subject at hand...
Basically, I think Ruzinus is correct: Players actually wanted to be Skinner-boxed.
The primary reason many players were dissatisfied with D3 (note: not a reason that D3 was a "bad game", because it wasn't, but a reason many players were dissatisfied - and I think some of that dissatisfaction is legitimate) is because it was harder than D2.
D2 was like a slot machine - it's really, really easy to repeat the process and try again for a win. This caused players to go on mindlessly and endlessly cranking that lever, over and over. With D3, they fundamentally made another slot machine, except this time pulling the lever takes a lot of effort. Players said they wanted a really really hard difficulty where the super-duper UBER best items would drop. Blizzard gave it to us, but Blizzard didn't really think about what the players were thinking.
Y'see, D2 wasn't a hard game at all, but because people like to pat themselves on the back, dedicated D2 players would lie to themselves and claim that what they did took a modicum of skill, rather than just rote grinding. Their super-leet-uber unique item sets were the result of their oh-so-hard work, not just the result of playing the game for ever and ever. So when Blizzard suggested making a (genuinely) difficult end-game, these players thought, "Yeah! We can continue to be the uber leet top-dawgz and show off all our phat lewtz to the WoW-noobz lol."
Fast forward a few months. People reach the end-game and get frustrated. The very vocal D2 fanbase - who were expecting things to be easy FOR THEM (not realizing that D2 was a terribly easy game) - weren't at the top of the heap, which filled them with uncontrollable amounts of envy. The same sort of player that wants to look down upon everyone else and laugh simply can't deal with the possibility that they were being looked down upon by others, which led them to the auction house. They soon discovered that it was easier to grind gold and buy items from botters than to find those items for themselves. So instead of playing the game as it was meant to be played, they play an easier version in which they go back to rote grinding, this time for gold instead of random item drops.
Now, I'm exaggerating a fair bit here about the playerbase, but this was the attitude in general. It wasn't only the D2 diehards that flocked to the AH - it was a very convenient feature for a ton of players - and the botters that were fueling the AH were themselves a tremendous part of the problem.
A lot of people have suggested that the inclusion of the AH was the root of the problem, and that's simply not true. Player trading and forum sales would occur regardless. The AH, however, was a catalyst for a problem that was inherent to the game for a lot of players: the best stuff was actually a challenge to obtain, and a lot of players actually wanted the game to be easy.
TL;DR version: Blizzard misread their fanbase, made the end-game too challenging for most, and didn't crack down hard enough on botters in the first couple weeks of the game (if that's even possible to do).