I suspect that too much is being read into the Star Wars case here: I'm not convinced it's typical. It felt to me like George Lucas was being given too much of a free hand, and so there wasn't anyone doing that checking, and that the interest was more in the 'event' of new films than their quality.

I also think that this post is more generally a bit muddled. The assumption seems to be that 'old' books are worse but that we hold them to lower standards, and I don't think this is true: it's certainly not demonstrated above. Nor is there any reason to think that LessWrong has a 'unique tool set' for good writing: Eliezer's post is in fact drawing on another writer, not cut from new cloth

As it happens, I'm also in an ambivalent position on HPMOR itself: I love it and find it really enjoyable, but I don't think it's fantastic as literature or in terms of characterisation. I think it uses lots of interesting ideas and is very good at sucker-punch or uplifting set-pieces (it can definitely make me laugh, cry, seethe etc.), but the feel of it is more a series of very effective sketches than a novel. Three Worlds Collide read very much like a very good SF short story to me though.