i know this is just my opinion, but evoker is the first new class they have ever added which wasn’t super cool and busted - in a good way - for the whole expansion it released.
death knight - it hardly needs to be said. ultra cool. always has been, always will be. their only down side was slow run speed. but wreaked absolute mayhem with death grip, anti magics, chains of ice. super powerful all expansion and got everyone excited.
monk - 3 amazing new specs that just about everyone was down for. came with panda race, also reasonably well received, although not a race locked class. mistweaver especially was pretty interesting and crackling jade lightning doing monastery healing was pretty good ranged dps option - for pandaria only - until it was nerfed. mistweaver honestly hasn’t been as interesting since pandaria, until dragonflight brought back better talent trees. i could say plenty on brew and windwalker too, but you get the point.
demon hunter - again, super cool. part of the legacy warcraft lore that got everyone excited to see made into reality. great mobility and double jump is always fun. strong the entire expansion. bonus points for being added in one of the best received expansions ever added to the game.
evoker, on the other hand… - and this is where naysayers to my view can go hard on the “that’s just your opinion bro” rebuttals, but, far as i can see, evoker in general are ugly. they don’t even look like dragons. just humanoid lizards. and it kind of looked like a phoned-in idea when most of the armor doesn’t even show up on the character model. this subsequently makes the human or elf visage form look less like additional customization, and more like simply a shallow attempt to plaster over the laziness involved. the “dragon” style mobility is rather underwhelming when all said and done. the “short range” spells is a desperate, almost farcical reason to come up with a way to label the class as innovative, but how does it make dragon magic more impressive when it has less range than any other magic in WoW? this just detracts from the prestige of dragons in this lore setting.
and when it comes to the “overpoweredness” of the specs, mostly this was not in the case of devastation. but augmentation was the first overpowered new spec that has created such drama in the audience. whenever you look at spell breakdowns for devastation and preservation, the list of spells is pretty small, with most of the power being in just 2 or 3 spells, it makes the class look incredibly simplistic.
simply put, of all the new classes ever added to the game, this one is the least impressive by far in terms of design, it has way too many drawbacks. its “good” parts like mobility are really not all that, and its not even visually impressive to look at, so i’m not surprised at all if its the least played, there’s no way people would stay interested in this class unless they really want to be a special snowflake for snowflake’s sake.