Yes and no. It was for sure much better than WoD. But it was not better than TBC and WotlK. So when MoP was the current expansion. Everyone said the same about cata before. IMHO MoP was better than cata. But in forums it seemed like everyone was like "ooooh cata was so much better than MoP" PvP wise cata was better than MoP, but overall i think MoP was better.
Nothing beats TBC and WotlK and of course classic, just because it was the feeling of a brand new game, nothing can beat that.
But i am pretty sure in LEGION no one will ever say, WoD was better than LEGION is. I can not imagine that, seriously.