Duchamp poked the art establishment in the eye with his 'readymades' (urinals on the gallery wall, etc.) Warhol with his 'factory' making silkscreens.
The 'reverse Monet' (too lazy to link) that caused such an uproar when it was shared last week was ironic – apparently people aren't aware that the impressionists themselves were considered 'not artists' by a lot of people at the time.
The camera and photography made many painters sit up and say, 'hey, it can't just be about "image" anymore' – enter abstract expressionism, fauvism, cubism, etc. Work that shifted the focus from the image represented in the painting ('a window into a world') onto the surface of the canvas itself: Rothko, Albers, etc.
The thing is, people have wild misconceptions about what this technology does. Many clearly think it's a photocopier. As if StableDiffusion is hiding copies of all these works inside. When in fact what's been done is to take all of this online knowledge and create an incredible new tool with it. Like a music synthesizer times a million.
It's understandable why this technology makes people uncomfortable. There are legit fears about displacement, economic uncertainty, etc. But we are fundamentally tool makers – it's arguably intrinsically part of what makes us human (borrowing from Carl Sagan's "Dragons of Eden").
If I were back in the art department last century, I'm pretty sure we'd be really excitedly discussing how these new tools will enable entirely new forms of expression. And sure, there'd be the old guard saying it was awful, and 'not Art'.
This is a really interesting debate – I just wish it scratched deeper than the surface more often than it does, with a bit more historical context.