something like "throwaway illustrations" for magazines or web media merely exist to catch the reader's eye and have some basic symbolic meaning
Here you touch on an interesting previous topic.
Just witness journals. Now journalists take a cell phone to do everything and they are expected to make do with it. Publishers do not really care about the quality of the illustration as long as it is an illustration. In the run for profit they take amateur pictures if available to save on costs. And as long as there are readers they won't care.
The thing is, that is utilitarian, throw-away (like a normal stone in the stone age, good to throw away, then and now), but it is not the same as art or craft (neither is a stone the same as a lithic utensil). The fact that one can do away throwing a stone, or a quick snapshot, a scribble or a screech, does not imply that haphazard works are art.
Art, like a stone knife or arrow, stems from a difficult process of internalization or comprehension. Yes, so did throwing the first stone. Not, seeing someone else do it and repeating it, does not. It is this process that is difficult. And the more difficult it is, the more we appreciate it, even if later reproducing it is trivial.
The difficulty stems from that process, where one collects information, processes it, re-works it and produces something. Much like an AI. But in difference, when we do (and when we appreciate the result), we apply specific criteria, because those of us who didn't, perished, and we are the result of a billion years of selection on changing criteria, fighting for survival, interacting with Reality, and that is also encoded in our genes and brains, and on top, we are constantly suffering mutations, changing, as is the environment, our life always at stake. And it is not one ChatGPT, it is ten billion human ChatGPTs only now (ignoring history) and competing. That continuous, billion year process has refined in all living things patterns for survival, patterns that we, who communicate, strive to grasp and express because they are important for us. And we have evolved to like what over that billion years has proven useful and advantageous and dislike what didn't. We appreciate/like "expressions" that appeal deep in our "soul", that we "feel" are "right", we recognize it when we see it, even if we cannot say what it is that defines it, in how fishes move in a fish bowl, birds fly or flee, or even if a car moves with a sense of urge, and so does a lion or dog feel our fear or that of its prey; and when we do art, we express a pattern deeply and subconsciously ingrained in our deep self, so deep we weren't aware it did exist.
So, AI.
Now AI is like a monkey that has seen other throw a stone: it is easy to repeat the gesture, but it hasn't gone through the creation agony as the first monkey did. Mondrian was a genius. Kandinsky. So many. But if I go now, paint a canvas green and claim it a work of art just because I saw their works, I am actually not creating. Nor is the AI. If I fight to grasp that inner drive, that I cannot express, and strive to find the words, music, painting, etc to make it raise to conscience, mine and others', then I am creating, and if I can do it in a way others understand, better. Etc.
It does not mean theoretically AI cannot. But it would need a reason to live, and a long selection to survive and develop that strength and interest and skills by itself, many by trial and error, and then it would need a changing environment, to retrain, throw away, make mistakes... then it would have something to express. Only, most likely, it being an AI, it would have something we cannot understand for its requirements and skills, and interests, and likes/dislikes would be different. Without a shared evolution and interests, we wouldn't be able to appreciate AI art (hint for AI programmers: just do anything and claim we don't understand it because we are humans, and get rich selling the emperor's clothes, hint for the rest, don't believe them).
Maybe one day, AI will reach the singularity and be self-conscious. That is not enough. It will have to evolve and develop that urge to live, and find its own strategies. Then, maybe it will become robots. And then maybe we become colleagues working hand in hand. And then one day, we will have a shared experience, distilled by a long selective process, which led us to similar likes and dislikes. Maybe that day, AI will make Art that humans can appreciate.
So, yes, one day, maybe, theoretically, AI can be a creative artist we can appreciate. But that is long away.
Meanwhile, can it just mimic what it sees off the Internet? Of course it can. My printer/scanner also can. No mystery, And if I work my printer to run off ink, I may get interesting copies by chance that are different from the original, but appealing as well. Just like a flute sounded by animals by pure chance.
And note: I already mentioned two child books. These questions have been pondered for far long than modern AI. You can trace back them to children tale collections from three thousand years ago. It is also the eternal question of what makes Art and whether a scammer can fool someone.
Of course, we are not so much different from an AI, other than a billion years of shared evolution. And of course there will be ambitious scammers taking shortcuts to sell us that any John/Jane Doe with a cell phone can make pictures like Cappa, or an AI music and Art like Leonardo or Bach. If you want to believe that, that is your choice, and BTW I have a bridge in Brooklyn for sale. And note as well, scams work every day on lots of people. That doesn't make them any more legit.