A personal anecdote, but I found generating AI images of my characters made them every bit more real and inspired things I would have never thought about before, which motivated me to write.
As an example, for Amelia Thornheart, I knew I wanted a blond, pretty woman in a side profile in a smart uniform:
Doing this not only made it that much easier to imagine my characters in my head, which translated to a smoother writing experience, but see that earring? I already have a scene planned around the earring, a heartwarming and cozy scene perfect for the budding romance/GL in the novel.
It might depend on what kind of writer you are, but for me personally, having an image like this helps tremendously, and I did it for free! Without AI I would be paying ~£500 to £1k for an artist to make something of equal quality, while not providing me any more benefit.
For me and the millions like me whose creativity is triggered by visual aids, AI is amazing. Whether generating AI images itself may or may not be an act of creative expression doesn't really matter to me, because the final product is something that triggers my own creativity, and that's what matters!