Ooo, interesting topic to talk about. I didn't watch your video myself (time), but I'm not a big fan of fanfiction (though it IS a great way for aspiring authors to get started in the world of writing - just don't plagiarized in the long run and it's golden). I think it's because of the amount of errors I typically find in them - it ends up highly annoying and ruins my enjoyment (why I stopped).
That's okay! There are some writers who have way too many errors and usually I'll stop reading if it's bad enough to take away from the story. Even regular authors make mistakes and I've gotten books from Penguin that are littered with a few (The Ruby Circle by Richelle Mead).