Wow! So, could you have written it yourself? Yes.
And you have explained yourself quite clearly, I understand the benefits that AI is giving you, so how does that play out for you? Get your questions so well-tailored that you need to intervene less and less? When does it stop being YOUR creation?
Not everything needs to be my creation. As I indicated, neither was the used adventure, Dungeon of the Mad Mage. Nor were the rules that is D&D and we use.
Think of it like this: When I walk out on the street, doe the pavers I walk on need to be handcrafted by myself? Does the bread I eat each morning need to be baked by my hand? Do I need to harvest the grain and grind it myself? Do I need to slaughter the pig for the ham? Do I need to raise the pig? Does every or any furniture in my house need to be handcrafted by myself? Do I need to harvest the planks, and dry the wood myself? Do I need to plant the trees?
I do not have to cook the meal myself to have a great meal. And would I care if a great meal was made by an expensive and famous head chef, or some unknown hole-in-the-wall restaurant by granny Chou? Heck if it was made by Walter the robot I wouldn't care either, the meal was great.
Undermountain in my case is dressing for a larger storyline. Effectively Undermountain and Skullport function as an 'open dungeon' in the same way an 'open world' functions. The problem is that it's too large to make detailed and atmospheric by human hands (or should I say it's not cost effective to be made as such by human hands). Quite often AI/LLM/generation is 'good enough' for the use case, it's far from perfect. But most adventures are far from perfect and most DMs are far from perfect, so why would my particular incarnation of an adventure try to achieve perfection?
As a DM I function as an orchestra director, I did not compose the music, I am not playing the instruments, I did not build the concert hall. I direct the performance for the guests, I'm in charge of the performance, I still take my bow after I am done. And the guest did not care that I did not compose the music, or played the instruments, my job was to give them a good performance.
In this particular case there's an overarching story arc besides the whole Undermountain dungeon, the Yawning Portal, and Waterdeep. Undermountain in 5e gives me enough rope to hang a TON of additional content. This gives me the room to work on that or not.
There is certainly a skill to getting AI to do what you want to do right, absolutely, and it is very useful for generating information, researching (although check what it comes up with) and developing ideas, certainly, but is that enjoyable? Do you find it rewarding on a Human level?
I think you overlook 'generating' in generating information/research. It's horrible for information/research, I only suggest you us AI/LLM when you already know and understand the subject material, because AI/LLM will halucinate at the weirdest moments and no one would know the difference if you didn't already know the material thouroughly. I will
not use it to analyze data, find answers that I don't know the answer too already, etc.
Now, due to the hallucinations, it's excellent for loose creative writing. And whether it's rewarding or not depends on the situation. It the goal is to build a ship, then using an AI/LLM/generation to build the ship might be unrewarding, but if the goal is to sail the ship, then the faster the ship is complete, the faster I can get started sailing. Journey vs. destination. Generally, AI/LLM/generation is about destination and not the journey. But for me part of the journey is understanding and learning about how to use these tools.
Again, it's a tool, it depends on how you use it and why you use it. Too many people misuse tools or don't understand how to use then and end up hurting themselves or others.
I write my own stuff, I draw my own stuff (it's not brilliant) and I love doing it - it's mine and I can be proud of it. I certainly don't make enough money out of it to pay for the effort I put in, but that's OK, I enjoy the process. Getting AI to do just seems such a wasted opportunity.
And if you're using AI because you can't afford the art, how will that play out? I The whole state of the creative process at the moment is being commoditised, there's less skills being learned and used, de-skilling the work force never ends well for the workforce.
If you feel you have to use AI to achieve what you want to achieve then I guess you'll go on doing it; you do you - but please make sure people know it's AI.
Let me be clear, being an illustrator is making commodities. If you've ever been trained as an actual illustrator vs. an artist, then you know that you're exactly trained to do just that, make a comoddity (and dress it up as art).
If/when I draw for the enjoyment of it, then I do that myself. If I need to illustrate monster X for the next session, AI generation is my friend! Previously I would have been going through existing artwork in monster books (which is why I have so many of them). And creativity can manifest in other things then drawing, creating jewelry, sculpture, painting, etc.
As for 'deskilling' the workforce, how many of the illustrators can actually paint with oilpaints? How about mixing their own paints? And everyone can take awesome pictures with their smartphone, has the art of photography disappeared? There are still people developing film, it's a lot rarer then 40 years ago, but it's still being done. Just like horseback riding...
I certainly will not hide it's done via AI, I've discussed it with then to a greater and lesser degree. No issues with it. But I wouldn't start with a disclaimer during my DM session "MADE BY AI!", number one it's not necessary with this group, and number two that throws the weight on the AI part and it's not important enough for that. Either people recognize it as AI or they don't. If they are not sure and ask, I'll not be lying about it.