For me (highly subjective opinion ofc) its that whole titan lore. Before it was more or less "down to earth" stories but who were connected to ICONIC VILLIANS. Draenor, Arthas, Deathwing were purely made out of love for the warcraft franchise (even WoD). MoP was great for being creative and something new, but then they started with that titan stuff... for me they lost it there, I have zero interest in all that overplanetary stuff... I loved Legion because of the legion invasion story connection to warcraft games but found the titan ending rather meh... and then BfA is centered around that... zzZZzzzz...