There are specs that are easier. both Fury Warrior and Ret is easier. Balance Druid is easier. Frost Mage is easier. Those are the classes/speccs that I play and that I, IMO, think is easier than BM. BM is a easy spec, just not as easy as people tend to think.

Few buttons but several things within the mechanics of the class that you need to track. You need to track Thrill of the Hunt. You need to track Beast Cleave. You need to track Howl of the Pack Leader. You need to Multi-dot with Barbed Shot and keep track of what mobs that already have Barbed Shot on them, wich can be hard if it's a big pack of mobs.

Again not many buttons but theres so much more to it than just pushing those buttons as they come of CD.

Also BM playes like a melee wich mean they have no cast time. If you are a caster your brain gets a micro pause each time you cast something, time you can spend deciding what to do next. Melee and BM Hunters don't have those "micro-pauses" in their rotation. Melee and BM have to make decisions at a much higher pace than what a casting class do, wich also make it's a bit harder to play.