For many, many years World of Warcraft's players have decried grinds. We've stated resoundingly that we hate gathering materials for our professions, grinding reputations, doing daily quests, completing attunements, how much time it takes to level, and more. Warlords of Draenor was the ultimate culmination of Blizzard's effort to accommodate us.
However, by addressing our complaints Blizzard created a game that couldn't hold our interest. They made leveling faster and easier than ever before, eliminated gathering and daily quests as necessary activities via garrisons, and made heroic dungeons effectively obsolete the moment you could walk into a raid. Pet battles, PVP, achievements, and all the new toys and mounts were insufficient replacements for activities that progressed our characters.
As a result, the huge surge of interest that drove subscription numbers higher than they'd been in years was lost, and then some. Blizzard took notice, and many of Legion's key features appear to be direct answers to the problem, recreating grinds and inconveniences that they'd finally eliminated.
Blizzard's answers will be imperfect, much as Warlords of Draenor's story and presentation thereof were imperfect answers to the flaws from Cataclysm and Mists of Pandaria. However, those answers will surely be improvements, and just as I was impressed by how far Blizzard has come from the utter inanity of Cataclysm's story, I am hopeful I'll be impressed by Legion.