In the abstract, I don't really disagree with you. It definitely wouldn't replace human made things or human perspectives, though. (which, as a human myself, I value highly). But I do agree that If I could have a genie show me the most beautiful picture possible according to my tastes, I would still be very interested in seeing it even if nobody made it.
This is a complete hypothetical though. The problem is that the generative models we have now aren't actually good at much of anything, beyond purely functional stuff like boilerplate text or code. (and even that is somewhat debatable)
Firstly, nothing these models produce is art, which requires a perspective that they do not have. It isn't valuable aesthetically or or in a literary sense, either; what is produced will always be bland and unchallenging. To oversimplify, it is the 'average' of the training data - nothing original or innovative.
I think one big issue that isn't talked about enough is that it can look okay at first, but is actually shit. It ends up being a kind of information poison. It makes it harder to parse information, because useless junk is no longer obvious. Like finding what looks like a fresh apple, but is actually just the skin with nothing inside. Especially with llms, there are so many ways it can be subtly bad.
What scares me the most is it improving in the future to the point where I can't tell and it's poisoning me without my knowledge. It's noticeable already - I've listened to podcast interviews where the guest has picked up on chatgpt mannerisms, and it's really eerie, because it's destroyed their personal voice and they don't even notice. "AI psychosis" is definitely a real thing, and I think it's also affecting a lot of people more subtly.
"How can I tell if this is slop so I can know to hate it"
While this is a bit of an exaggeration, I see why you dismiss this at first. However, it's someone recognizing that they may not be able to sort high quality information from low (or not wanting the burden of doing so). Knowing it came from a human not only means it has some inherent value, but also means that we will be proficient in judging and sorting our own informational input.