I'm expanding on the author's point that the hard part is the input, not the output. Sure someone else could produce the same output as an LLM given the same input and sufficient time, but they don't have the same input. The author is saying "well then just show me the input"; my counterpoint is that the input can often be vastly longer and less organized or cohesive than the output, and thus less useful to share.
To be fair, the first Harry Potter is a kinda average British boarding school story. Rowling is barely an adequate writer (and it shows badly in some of the later books). There was a reason she got rejected by so many publishers.
However, Netscape was going nuts and the Internet was taking off. Anime was going nuts and produced some of the all time best anime. MTV animation went from Beavis and Butthead to Daria in this time frame. Authors were engaging with audiences on Usenet (see: Wheel of Time and Babylon 5). Fantasy had moved from counterculture for hardcore nerd boys to something that the bookish female nerds would engage with.
Harry Potter dropped onto that tinder and absolutely caught fire.
The world-building is meh at best. The magic system is perfunctory. But the characters are strong and the plot is interesting from beginning to end.
It certainly wasn't the writing that elevated it. I think it was as simple as tapping into an audience who for once wasn't raised as some nuclear family. a Cinderella esque tale of being whisked away from abuse mixed with a hero's journey towards his inevitable clash with the very evil that set this in motion.
The movies definiely helped too. The first few were very well done with excellent child actors. Watching many other fantasy adaptations try to replicate that really shows just how the stars align into making HP a success.
This has already been the case for decades. There are probably brilliant works sitting out there on AO3 or whatnot. But you'll never find them because it's not worth wading through the junk. AI merely accelerates what was already happening.
I think "merely" is underselling the magnitude of effect this can have. Asset stores overnight went form "okay I need to dig hard to find something good" to outright useless as it's flooded with unusable slop. Google somehow got worse overnight for technical searches that aren't heavily quieried.
I didn't really desire such accelerations for slop, thanks. At least I could feel good knowing human made slop was learned from sometimes.
Fairly or unfairly, people (including you) will inexorably come to see anything done with AI as ONLY done with AI, and automatically assume that anyone could have done it.
In such a world, someone could write the next Harry Potter and it will be lost in a sea of one million mediocre works that roughly similar. Hidden in plain sight forever. There would no point in reading it, because it is probably the same slop I could get by writing a one paragraph prompt. It would be too expensive to discover otherwise.