The biggest change came in the character system. While Diablo II was about picking stats and skills as you level up, Diablo III focuses on flexibility, offering a range of skills that can be freely changed at any time.

Each character has six slots for active skills and three slots for passive ones (four with the expansion). If at any time you're unhappy with your character build, you can easily change it. Each active skill can also be equipped with a Rune, slightly modifying the skill – reducing cooldowns, changing damage types, adding more effects, making it last longer and so on.

A more controversial decision was that Diablo III required an Internet connection, even for single-player, which led to some huge server issues on launch.

Another disappointment was the game's difficulty, divided into four modes you had to unlock one at a time. Many players (myself included) got burned out by playing 15-20 hours of an incredibly easy game before begin allowed to try a harder difficulty. And there was no endgame besides a pointless grind.

Yet, what nearly killed Diablo III was a single, greedy idea: adding an in-game Auction House.

It was made for players to sell their loot, not only for in-game currency, but also for real money – of which Blizzard would take a cut. To be sure people would use it, rare items were dropped sparsely. You could play for hours without seeing a single good drop. And when you got one, chances were that it was for another class, pushing you to sell it at the Auction House for something you can actually use.

Furthermore, the damage of every skill and ability was tied to your weapon and gear, making even the best player useless without decent equipment. Progression became inherently tied to the Auction House, the best items selling for over 50 dollars. Diablo's “kill and loot” gameplay loop was broken.