I think you are wrong about the quality of fan fic and the ethics of its writers. Though you are right as well. I think that ethical standards are laxer than they were in the past, though a discussion of why this is would probably take more space than available in comments. I'll just point out the amount of plagiarism, bad behavior, and bad writing reported among published authors and note that it would be a lot worse if not for the editorial gatekeepers.

As I have read more I have become both more and less tolerant of fiction in general. I think the main problem with fan fiction is that it is like reading the slushpile straight without editors in the way. Crossed with a writing group that does not actually want to improve writing, but to just make friends and socialize.

In short: If I were to write a rant against fan fiction it would be fairer and a lot more hard hitting than hers.