Seems to me that the change happened around Wrath. The game used raiding as it was intended as a small part of endgame content. Then they wanted more players raiding because the devs liked raiding, and felt that raiding could build a better game, and raiding requirements were lowered. They tried to become more hard in Cata and got immediate pushback. MOP made things more flexible, but still carried the emphasis on raiding, WoD was pretty much the raid or die expansion, Legion offered a ton of things for players but didn't get moving until the last patch, BFA tried to expand legions techniques but failed, and SL tried to go barebones with more emphasis on raiding and a bunch of casual players left.
I'd hate to say but Ion probably needs to go. Who I think should replace him? Is someone who's been around the MMORPG market for a long time but has spent significant amounts of time not around high-end players