I don't care about "acceptability" personally however I have tried a bunch of different flows for AI generation of assets and will likely use them to some extent in the final product.
The main issue comes to coherence. With code the coherence is strictly syntactic not semantic it's just about symbolic relationships and those are what LLMs are good at. An LLM implementing a piece of code with 0 preparation is likely to be indistinguishable from an engineer writing in manually. Coding itself is just the representation of syntactic relationships. The variables are true or false, that's it. Whether AI writes it or a person does if the variables end up in the right state at the right times it's insignificant especially if it's the same person structuring the code and just gets the AI to write it exactly as they would.
For AI generated assets getting coherence in terms of art assets not even just say like character art design, but artistic coherence is much broader and hard to make explicit. What is it that makes the colors, texture, models and animations work together well? What is the relationship between having an item with a specific color and texture in a specific context in relation to all those other items? That's essentially the question of what good art is and it's far more intuitive you could attempt to formalize it but someone can just disagree with your formalization and you can't really say anything.
Getting art that is coherent with the rest of your work depends upon having someone who is able to internalize it and express it. I personally don't think AI will ever be capable of that however I do think we will likely end up in a place where a good artist could leverage AI to produce far more assets then they could have individually. It will depend on them feeding it a bunch of structure and criteria and evaluating what it does though.
How can an AI understand enough about your character and his role in the story such that his personality is conveyed through his animation, his gait, his voice acting, the materials and clothing, etc. It's just not a strict syntactic relationship which is what AI is actually good at, there is no way to actually formally represent that.
The issue with AI generated assets for me is that they are just bad and ugly and being used by people with bad taste. I can see a future where you have technically competent artists having AI tools they can train or set up to reflect their vision and be closer to their work following principles they establish but we aren't there now. For coding because it lacks that a well written program by a human or AI (guided by a human) is basically identical. I could say an AI designed game would probably be awful for similar reasons that AI is or purely vibecoded things that are artistic like shaders, specific mechanical tuning, etc for the same reason AI art is bad. Those are also much easier to tune because they are at the end of the day symbolic formal representations that can be easily manipulated by AI.