Buddy, I get it, and I agree with the idea that "AI", the way that it's being made today, is unethical(while also having a problem calling these database processing programs "AI", since frankly, they're not), but this dev is NOT some unethical pseudo artist peddling other people's art as their own, they are, as a matter of fact, creating their own creative endeavor, one step at a time, they're simply using "AI" art as a crutch to get their vision going.
There WAS a time in the past where perverted indie game devs had done the same, only replacing the "AI" art with essentially stealing others art and at most simply giving them credit, if even that. Slavemaker is the first that comes to mind. Regardless, the only difference between that and this, is that there's a mid-point which allows for greater creative freedom with the added caveat that said point, that being the companies that made the "AI", do not even give credit to the artists whose art-styles they emulate, preventing creators, such as the dev here, from giving credit where credit is due if they wish to benefit from the additional "freedom"(for lack of a better word) that "AI" art provides. There's also the qualitative cost, but that's a moot point in this discussion.
Significantly, however, and if you'll listen to nothing else, at least listen to this, you must remember, the dev is spending some of the money they've earned from making a game based on "AI" art, something you've established takes money making opportunities away from artists who need it, to commission art from the very people "AI" art is meant to be depriving, something they likely couldn't finance initially for obvious reasons.
Once again, cause I like hearing myself talk, they're using the very tool that would normally hinder an artist's ability to make money to fund commissions that make money for artists. Like it or not, "AI" is here to stay, it very likely will never go away, no matter how much we screech and howl. People like the dev, though I'm certainly not claiming they're doing it on purpose, are exactly the sort of way "AI" art SHOULD be used, potentially only 1 of 2/3 ethical ways you can use "AI"(the other being personal use or for actual creative inspiration, which I'm not sure if it should count as its own use), since it provides the funds for an independent creator to finance the very victims of this tool.
I get it, you're passionate about this, but the person you've been ranting at is also someone just trying to scrape on by, and while there is some room to debate as to whether or not they deserve criticism for relying on "AI" art, you need to also give them props for what they have created outside of that. They are, after all, in the same category as those who would suffer in the prominence of AI, an independent individual trying to bring their own vision to life. At the very least, you ought to recognize that.
tl;dr: Dev's used the bane of artist's commissions to make money to commission art while bringing their own vision to life, and I think that's kind of poetic, yeh?