The universal complaint about Warlords nearly from the start was that there was nothing to do after leveling and finishing your Garrison if you were not interested in raiding. They dropped from over 10,000,000 subscribers to 6,000,000 in just nine months. That's not raiders. That's casual players with nothing to do. Warlords was a fairly decent expansion for raiders for the first 15 months or so.
Polygon wrote a decent article about it which I would recommend reading if you haven't. Patch content was sparse and the 6.1 patch wasn't really a content patch at all.
After that, Hazzikostas was very careful to say any time he could that Legion would have plenty of stuff for casual players to do. And it did. They more or less followed that pattern with BfA (perhaps too closely). I don't believe that BfA is the worst expansion ever. I think it's a middle-of-the-road kind of expansion myself. But there is stuff to do. And Shadowlands promises another campaign-style quest line and the endless dungeon thing along with the rest. I'm sure there will be a bunch of patches as well and how that works out remains to be seen. But I expect there's going to be things to do.
So that's why I think Warlords was a sort of watershed for Blizzard and casual players. People can disagree with that but there's a lot of strong evidence that the increased team size was substantially about more non-raid content.
I do think that Hazzikostas understands what the game needs. I don't know how well that gets implemented into the design. Almost by definition, WowCraft game designers are not casual players so they are guessing as best they can two years in advance what casual players are going to like.
The one thing I think they've missed is professions. There maybe should be a team that just does nothing but professions. If you want to keep casual players around for a long time, allow them to be makers and sellers. Make professions something that you need to be in the world to do properly. It's a missed opportunity for them. Even something as dismissed as archaeology could be interesting if they would simply tell stories through the artifacts. Stories are good things. People like them and to discover little arcane points of lore.