I guess your point is that a camera, a paintbrush, and an LLM are all tools, and as long as the user is involved in the making, then it is still their art? If so, then I think there are two useful distinctions to make:

1. The extent to which the user is involved in the final product differs greatly with these three tools. To me there is a spectrum with "painting" and e.g. "hand-written note" at one extreme, and "Hallmark card with preprinted text" on the other. LLM-written email is much closer to "Hallmark card."

2. Perhaps more importantly, when I see a photograph, I know what aspects were created by the camera, so I won't feel mislead (unless they edit it to look like a painting and then let me believe that they painted it). When someone writes with an AI, it is very difficult to tell what text and ideas are originally theirs. Typically it comes across as them trying to pass off the LLM writing as their own, which feels misleading and disingenuous.

I think you are right that it is a spectrum, and maybe that's enough to settle the debate. It is more about how you use it than the tool itself.

Maybe one more useful consideration for LLMs. If a friend writes to me with an LLM and discovers a new writing pattern, or learns a new concept and incorporates that into their writing, I see this as a positive development, not negative.