Why did people like Mists so much?
- They changed the talent trees to such an extent that the 'core' aspect of them, present since Vanilla, was completely taken away from players. Sure, there were cookie-cutter builds, but that hasn't changed with the new ones, has it? Alongside Cataclysm it was one of those expansions where pruning and dumbing the game down reached new levels.
- It was extremely goofy. Fish-people, monkeys with bananas, drunk Panda-men, small rabbit-like creatures, etc. It was difficult to take it seriously. Blizzard always had fantastic humour, but this was always backed-up by an otherwise serious setting, Mists of Pandaria felt so over the top.
- Scenarios. These were essentially AoE zergfests with little to no strategy or communication. They were just blind runs with zero interaction needed between players, hence they felt even worse than dungeons.
- Zone design. Other than the Jade Forest and Kun Lai Summit, the other zones felt incredibly dull and looked sub-par. Specifically Dread Wastes (yuck), Townlong Steppes and the Krasarang Wilds. The zone design just didn't cut it out for me, including the quests and overall story.
To each their own, but I really didn't like MoP. Perhaps it was an issue with me and not the game (i.e. I wasn't feeling the magic anymore and was burned out) but I can't say I miss it. I prefer the theme of Legion up until Argus.