I don't think the author is posing as a professional. These models are like having a 3D printer at home. Very handy in a pinch, but what they make doesn't replace the real thing.
The problem isn't that they look shitty to pixel artists or experts, they look shitty for anyone with a bit of observation.
It's junk art the same way Mc Donald's is junk food.
I think we could do a bit better here with the explanation of what looks bad to you..
- the magenta background is still visible along the edges - the color palette is all over the place - random noise pixels of totally different colors are visible scattered around - the lighting and shading doesn't look that good
There's plenty of real food that is as heavy and as salted, and as such no healthier, than junk food. But it actually tastes good. (I can't exactly put the finger on what makes an Italian pizza better than a US 7/11 one, but it's not about the former being healthier).
I just don't get the complaints about "use proper art" when it comes to games. Most of the time the game has some other, far more glaring, visual issues (anti-aliasing, clipping, icons-not-matching-items).
I have a suspicion that when you're looking at (and generating, because you then look at the results) AI generated images and text more you get desensitized and are more likely to say that something looks okay when to other people it won't.