AI generated content is often seen as low-quality (depending on the model used) and can lead to spammy, low-effort content. Many people also have strong opinions about it and get into arguments about whether it is acceptable or not, or whether AI generation makes you a bad or stupid person, whenever people post it. I'm not prepared to deal with and breakup these fights, so we just opted to not have it in this community to keep people happy.
If there is enough interest I might consider creating a community for AI generated dragon content on lemmy.dbzer0.com, and recruit moderators from the other AI communities there. If that happens I'll update the sidebar to link to that community as the place to go for AI generated dragons.