For me the line is the cost of the AI tool: if it requires running on a datacenter and training with massive amounts of data obtained without consent of the creators, it is too costly for memes.
Other applications might have extra criteria, for example, I’ve seen nature enthusiasts point out that “enhancing” photos of animals might modify the photo enough that the animal loses its defining features
I pay for games instead of pirating because I believe that the people that worked on a game deserve to be compensated for their work. If these people are using generative AI that was trained with images obtained without the consent of the creators (and right now it’s very unlikely they are using ethically-trained generators), they are not paying the artists that helped create their images. Why should I pay for the game then?