I agree with some other comments that this is a question of public domain vs. copyright. However, even copyright has exceptions, notably fair use in the US.
TL;DR: If I can create art imitating [insert webcomic artist here] based on fair use, or use their work for artistic inspiration, it's legal, but when a machine does it, it's illegal?
One of the chief AI critics, Sarah Andersen, made a claim 9 months ago that when AI generated the following output for "Sarah Andersen comic", it clearly imitated her style, and if any AI company is to be believed, it's going to get more accurate with later models, possibly creating a believable comic including text.
Regardless of how accurately the AI can draw the comics (as long as they aren't effectively identical to a single specific comic of hers), shouldn't this just qualify as fair use? I can imitate SA's style too and make a parody comic, or even just go the lazy way and change some text like alt-right "memers" did (politics and unfunniness aside, I believe the comic should be legal if they replaced "© Sarah Andersen" with "Parody of comic by Sarah Andersen"). As long as the content is distributed as "homage", "parody", "criticism" etc., doesn't directly harm the Sarah Andersen's financial interests, and makes it clear that the author is clearly not her, I think there should be no issue even if it features likeness of trademarked characters, phrases and concepts.
Makes me ashamed there is a book by her in my house (my sister received it as a gift).