Good point XD
I feel like the first thing you write down off the top of your head is pretty close to everything that's already out there; only one inference step away at most; so it'll usually be 'basic', 'obvious', 'done before'.
Reflecting/'rewriting' your story is like having a dialogue with yourself. You've commented on what you've observed in the world/other people's stories, now you comment on your commentary, and then comment on your commentary on your commentary, etc.
(And incidentally, a lot of stuff I've read that struck me as insightful are from niche communities that aren't very visible from the outside that I've never got the chance to learn about, but have been engaged in internal dialogue for a long time since before I was even born :P)
They say 'you can never truly be original; there's nothing new under the sun', and I do agree that it's kind of inevitable to start in an unoriginal place -- but clearly we perceive some works to be more original then others? 
I'm beginning to think the factor here is how many inference steps away your work is to 'common wisdom', or at least the stuff your reader is familiar with.
TL;DR - the longer your ideas spend developing in your head/harddrive/notebook/etc, the more 'original' it's likely to be 
