Maybe I'm mistaken, but I don't think it's a Nostr problem specifically. I don't go to other social platforms, except for some group chats, but I do see AI art in so many real world non-Nostr places these days. The group chats are also full of it. But it's all expected given that most people always loved horrible premade meme images before AI was a thing. Also people talking to AI chatbots are a thing worldwide, or so I'm told. It's hard to imagine but I do believe there are millions of people who just open ChatGPT and have long conversations and find them interesting.

Generally most people dislike ai art, it is used for memes and whatnot. But the prevelance here is somewhat unusual. You won't really see this many AI art avatars anywhere else. Also yeah AI chatbot usage is huge. But I'm saying ai reply bots. Pretty much any other social media that had chatbots reply to you unbidden would be seen as a spam attack, on nostr it's "interesting"