Purely anecdotal but I do think there is more AI fic proportionally speaking in bigger fandoms, especially those that grew rapidly and/or whose growth came in part from non-fandom people who are fans of a ship rather than the show/book/movie/etc. My pet theory is that it's because what used to just be really bad first-time fic writing from inexperienced fans is now just AI slop, but it's the same underlying demographics doing the "writing." For example I used to be in the 911 fandom and there were loads of people who came to fandom for the main gay ship and that alone, and they came from places like TikTok or Twitter. And for the most part they were not good writers or actually fans of the show. So a majority of the fics in the fandom, even six or seven years ago, were just terrible. They were definitely written by real people, but the fandom caught a lot of people who were new to fandom and to fic, and who in many cases were mostly just looking for generic yaoi writing, so they hadn't necessarily developed craft or taste yet. And I don't know that many of them wanted to do that, because they--again--were mostly looking for and amplifying just really bad writing.
Anyways I ended up leaving the fandom because I got tired of wading through bad fics. Popped back in there recently just to see what's up and it's the same proportion of bad fic to good, only now it's mostly ai instead of people-written. And the AI fic is doing the same stuff as the bad writing years ago--generic yaoi with the main ship, whump for the fandom fave, etc. I checked out Heated Rivalry which had a similarly ship-driven popularity explosion and it's the same thing; the F1 fandom is too. Some of my smaller fandoms and also, weirdly, the Pitt fandom, seem to have a relatively lower proportion of AI slop...but they seem (to me) to have more participants who have been in fandom a while and who are fans of the show/book/movie/etc in general, rather than just there for a particular ship. See for example HRPF, where the current viral ship has a higher proportion of AI fics than other stuff posted within the same time frame.
I've also found that certain tags tend to have more AI fic than others. Hurt/comfort and enemies to lovers seems to have more; stuff relating to gender seems to have less. A/b/o dynamics tends to have more; non-traditional a/b/o seems to have less. Stuff tagged angst seems to be more AI-ified than the stuff tagged grief. Really anything that lends itself to whump or woobification of a popular character is going to have more AI, stuff that suggests nuance and complexity has less. Personally I think it's because the more "intellectual," for lack of a better word, tags seem to draw writers who want to engage with something and are using fic and tropes to do that, vs people who just want straightforward tropey stories, usually with a shipping lens. But these are more or less the same trends I noticed re: good/bad writing pre-AI, just with a higher volume of fics to parse through.
In other words I think the AI thing is just inextricable from the dynamics of fandom going mainstream. There's always been the bad-writing, new-to-fandom contingent on Ao3 and elsewhere, and they've always been bigger in more widely accessible fandoms. It's just that now they're using AI instead of writing themselves. And because that takes less effort, and because fandom in general is more widely accessible now, there AI stuff feels like an avalanche. There's just fewer barriers to entry for that kind of lazy participation now. AI facilitates surface-level engagement with fandom, but that surface-level engagement isn't itself new and has always been present to greater or lesser extents depending on the source material.
And I don't mean to be down on new-to-fandom folks or people who are new to writing! I'm just trying to, very generally, get at a dynamic I've noticed in who participates in fandom and how they get there, and how those things shape the output we see here and on AO3.
this is super, super interesting, nonnie, i really appreciate hearing your breakdown!
it's interesting to think about the different ways that people come to fandom. when i was like 11, i honestly think i first found out about "fandom" in what would have been considered mainstream at the time ways, which is like i was at a friend's house and we were in a chatroom (because i wasn't allowed to go in chatrooms) (also i hated it) and there were people posting horrible manips of backstreet boys doing gay sex to each other. and then i think my friend showed me this story about backstreet boys on the titanic, and like technically it was fanfiction but it was done in that mean way where the intent is to mock?
so all of that was the late 90s version of seeing fandom on twitter or tiktok, i think, like the mainstream entry into it.
i guess now, instead of the parady stuff, it's most of like... thirst trap through shipping? like on insta i'll see reels where the point is to show how hot the drivers are, and then the random landoscar ones that come up on my feed have the same sort of feel to it?
but i get the feeling in certain ways that the attitudes around fandom are similar to how they've always been, in that most people know it exists but don't engage with it (though i think more proportionately it's more people), and then there's a surprisingly large segment of people who engage with it in the most socially acceptable ways, which i think was and still is having like a famous person/ofc. because then it's like just the romance novel self insert fantasy. like when i found out stories on wattpad were getting millions of views and were so popular they were getting turned into books and movies i was sooooo shocked.
i guess now the thing that's changed is there's also an overlap to that more socially acceptable engagement with fandom that also includes reading m/m shipping fic? and 911 is a great example, because it's a super popular show on network tv that is hot buff guy on hot buff guy and they're hot and buff in that way that appeals to straight women. vs. say like david and patrick from schitts creek, were it was an irl queer person playing one role, and the appeal of that ship (i think!) was the feeling of genuine queerness. which isn't to say there aren't wonderful queer 911 fans, because obviously there are, but it makes sense that there would also be that significant normie appeal.
anyway, this is a bit of a tangent that you just got me thinking about with your interesting ask, because i think in all scenarios there is "bad fic" in that writing is hard and it takes a lot of time to learn how to do and all of us write less-great stories before we're able to write more-great stories. but i think maybe there's a difference in levels of unhinged in more queer spaces vs. paint-by-numbers-tropes in spaces where the appeal is that predictable romance-genre-style of writing.
so yeah, all the stuff you said about different tags having a greater proportion of ai generated fic makes a ton of sense, and - also anecdotally - does align with what i've seen. you can't use ai to write insane and unhinged, or to subvert a trope.
we were talking a while ago about the shift in fandom to write omegaverse straight, and by that i mean literally straight feeling as in het feeling hahah but also straight as in the trope is taken at face value and not subverted in anyway. and i'm realizing how that at least some of that is likely because of how often those stories are ai generated.