I actually kinda agree with their assessment. When you hit level cap in WoW, the only thing left to do is raid with 9/24 other people. Sure there are dailies and quests and 5-man dungeons, but Blizzard mostly focuses on adding raids. Every big patch (x.x.0) focuses on adding a raid, and not a 5-man dungeon or questing hub or anything. Your casual player can't do 10/25-man raids every week.

They're also removing 2 mount rewards from 2 achievements in the next big patch, because people who raid the higher content will find those achievements easy to get. If you're a casual who raids very slowly, those 2 mounts are now denied to you, despite the challenge still remaining for you. That's content removed for casual players who like to collect pets and mounts. So yeah, hardcore raiding is what primarily drives Blizzard's hand these days.