I don't understand why this isn't a thing yet. It's going to be. At some point it's simply going to take over everything. The potential is just too astoundingly great. I'm not an artist but just experimenting with Stable Diffusion for just a little bit has shown how vastly superior AI art is over DAZ it's downright scary. The only thing is that an artist needs to manually fix hands and feet. But more experienced artists needs to chime in on the situation and contribute to the conversation.
By the way, forget DALL-E and Midjourney. It's about Stable Diffusion run locally on your PC. Then again I believe there is something called OpenJourney which can be run locally. The technology keeps evolving.
There are a few factors I think are at play for this not getting that much adoption YET.
To run Stable Diffusion locally you need a few specific GPUs at the moment, so cost might be one thing.
Then you can always run into various issues that would mayhbe turn off an artist to investigate unlike a developer that might get a turn on investigating what's wrong.
Then you have the difficulty of getting consistency. You can always train a LoHa or Lora to have more consistency across diffusions, but that is also something that an aritst might be turned off by since it can get quite technical to get a good Lora made.
Then you need to use all sorts of tricks either via prompts, size, inpainting, outpainting, etc to create a good scene.
Then you'll get a debate over if it's really art and all sorts of moral conversations of wether to hate the game or love the game that uses such methods for generating content.
All of these are in a constant flux of change as the field has been progressing exponentially over the course of a few months. I'm up for collaborating with anyone that wants to use these methods in creating a game but I think it will take some time for most people to catch up to this tech at the moment.
Iirc OpenJourney is another Stable Diffusion model which tries to create content similar to Midjourney, it's not quite there yet though. For extremely creative stuff Midjourney still has an upper hand.