The criteria for a work being copyrightable literally is the slightest touch of creativity, and I'm quite certain that writing a prompt and selecting a result out of a bunch of random seeds would qualify for that.
Fully automated mass creation would get excluded, as would be any attempts to assert that copyright to a non-human entity, but all the artwork I've seen generated by people should be copyrightable - the main debatable question is whether they're infringing on copyright of the training data.
On a different note, I'd argue that the models themselves (the large model parameters, as opposed to the source code of the system) are not copyrightable works, being the result of a mechanistic transformation, as pure 'sweat of the brow' (i.e. time, effort and cost of training them) does not suffice for copyright protection, no matter how large.
> The criteria for a work being copyrightable literally is the slightest touch of creativity
If a prompt is copyrightable, that's a problem. Because it's just words. Recipes should be in the same league then.
If I can get the same output with a slightly different prompt, how would you protect your works?
If I copy your output, how can you protect your works, given that the output depends on something not copyrightable? (as per your statement, which I agree with)
Look at it this way: If I make something out of a Spirograph, is it a copyrightable work?
If you are an artist you can't claim any copyright on what you're generating.
If you're not the copyrighted holder it follows that you can't sell it or that you can't complain if someone else copy it (verbatim) and sells it.