Yeah, rules. Every fantasy world has rules.
Middle-Earth has rules. Gandalf can’t just insta-kill Sauron from halfway across the world. He needs to do the things one must do in order to beat the Dark Lord. Otherwise there wouldn’t be a story, nor any compelling mythos behind the Istari (wizards).
Harry Potter can’t just look at Voldemort to cast spells. He needs to weave his wand and say the words of his incantations, or it won’t work.
Narnia isn’t accessible from every wardrobe in the world. It’s accessible from a specific one. If it was, “the” wardrobe would lose its charm.
Star Wars has almost exclusively 70s sci-fi tech, because those are the rules of compelling and believable Star Wars.
While Warcraft as an IP takes itself a bit less seriously than these other examples do, it still needs to adhere by its own rules.
Orcs aren’t blue, they’re typically brown, grey, or green. For reasons we all know.
Connecting this back to transmog, then, and anyone should be able to agree that there are probably not any craftsmen on Azeroth able to create some of the transmogs we’ve seen recently, or even concieve of them as concepts. For example all the heart-stuff from February. Those are clearly inspired by western society IRL and our ideas of Valentine’s Day and fictional characters such as Sailor Moon.
I’m not entirely against “fun” transmogs, though. Some of the stuff we have now is OK. I’m not lying in bed at night, pondering the implications of the Yeti outfit.
But I think, and especially for as long as Blizzard keep insiting Tanks shouldn’t be able to wear Cloth because of reasons, it wouldn’t be good for the game if everyone ran around in completely silly outfits, all of the time. For example, why is it possible to tank a raid looking like a Murloc, but not looking like Geralt of Rivia? (A Warrior in Leather armour.)