They've been listening to players complain for years about how Uniques, Sets, and then Runewords made the game bland, because everyone was searching for and wearing the same items, and how it put such a final goal on the game. People have been asking for Blizzard to make high-rolled Rares better than Uniques for a long time. So that's what they did, and now people complain. What gives? Listening to the playerbase just seems like damned-if-you-do, damned-if-you-don't.
People wanted Inferno to be hard. It was supposed to be an 'endgame' mode, something that would take months, if not years, to develop the skills and farm the gear to be able to beat it. That's what people asked for, that's what Blizzard delivered, and what do we hear? People expect to just cruise on through it, just equipping whatever they find on the first run like normal mode and beat it within a week.
People complained that the most efficient farming method in Diablo II was running bosses over and over, and that there was no reason to go explore the rest of the game. It was boring and repetitive, with little chance for what you wanted to drop, because you were looking for a specific item, and it had less than 0.01% chance to drop. So what does Blizzard do? Make random, challenging fights in random places through the game. Elite monsters and events, so you wouldn't get bored. And now people complain that scripted boss fights (while cool) should drop lots of good stuff every time you beat them? They want to just mindlessly farm the same thing for hours on end?
While you may disagree with the exact details on how Blizzard designed Diablo III or accomplished those goals, I don't see how anyone can complain that they haven't listened to their fans. If you've been paying any attention to the Diablo community over the past couple years, there should be no question as to why they did what they did: it's what people asked them to do.