Really? What makes HPMoR not good enough to be publishable?

50 Shades of Gray was a twilight fanfiction, and apparently it was good enough to be publishable.

What does it actually mean for a piece of fiction to be 'good'? HPMoR can be an author tract at times, but it also has one of the most intricate plots I've ever read, specifically designed so that thinking about it with knowledge of bayesian cognition and rationality allows the reader to discover more things about the story. There aren't many stories like this.

What about the actual quality of the writing isn't good enough? I would say it is at least as good, in terms of whatever it is that makes me enjoy it, as 80% of all fiction I've ever read.

And sometimes when I read Humanism Part 3 I think it's better than 100% of other fiction I've read.