And canvases and paint have existed for even longer, but it needs someone skilled to make use of it.

Stable Diffusion enabled the average lazy depraved person to create these images with zero effort, and there's a lot of these people in the world apparently.

So? At the end of the day, regardless of how skilled one has to be to use it, a tool is not considered morally responsible for how it is used. Nor is the maker of that tool considered morally responsible for how it is used, except in the rare case where the tool only has immoral uses. And that isn't the case here.