IIRC WW monks were awful in MoP for a while, but then saw some buffs. I feel some classes have longer droughts than others, but for the most part each class has one viable spec.
Also have to take into account rating. Some people get stuck at 1700 and blame the fact that they are playing an A or B tier spec, which obviously is ridiculous. I think for the most of the community, unless you’re at the top of the top, most classes have one viable spec. But monks have been good for a long time.
Viable =/= meta. Most, if not all, classes always have a viable spec.