Not to mention that it could be a legal minefield if your designer uses AI.

> everyone can tell and it looks generic when AI is used

For now. I feel like the gap continues to close with each release, and it's only a matter of time before it becomes indistinguishable.

alternatively, you can use AI as a starting point. All design is iterative.

Well, you can definitely make AI art much less obvious with the right tweaking (directly running models, blending different sub-models, etc). The bigger issues from a professional perspective are liability concerns and then, even if you have guaranteed licensed sources, the impossibility of controlling fine details. For a company like GW it's kind of pointless if it can't reflect all the decades worth of odds and ends they've built both the game and the surrounding franchise around.