Unless you've done an exhaustive reading of the fanfics, you're missing a couple gems in the bunch--Jiara's works, and Machievelli's SW: The Beginning and Republic Dawn (the punctuation needs work but he says he's posting without editting, so I don't let it get in the way of what is an otherwise very entertaining series.).
A lot of the writers are very young and/or are writing fiction for the first time or two and thus are learning (and I'm in that latter group myself). We're making neophyte writers' mistakes that really affect quality. However, the only way to improve is to keep writing. The forum here is remarkably patient and encouraging with those of us who decide to post, which takes no small amount of courage, especially the initial time.
I'm not a big fan of all the stuff Mach reviews (either for content or style), but when he says it's well written, he's nearly always correct.