For me it is a lot of the retcons that came in with Chronicle. Particularly those concerning the relationship between titans and Azeroth.
The trolls being one of the only native beings that were around before the titans arrived was a huge part of what made them interesting. Now they are just another product of the titans messing with the planet. As is all life. Nothing on Azeroth is truly natural anymore, it’s all a product of arcane meddling.
I also really dislike the Wild Gods needing Freya to tie them to the Emerald Dream. Diminishes their role and makes them seem less powerful than even the titan’s constructs, which is a shame seeing as they are supposed to be the cosmological avatars of of one of the defining forces in the mythos.