It seems to me that with the more practice we all have writing fanfiction, the better it gets -- as with practicing anything.
One thing learned through time of writing and writing and writing is subtlety. Some of the absolute drama in my fiction has been carefully weeded out over the years. Fiction has to retain some sort of subtlety to bind the working forces of it together. There are so many factors in writing fiction -- characters, plots, even word-choice -- and to bind them with dramatacism is to ruin the good basis you've worked so hard on.
Writing really is a tough thing, isn't it? We talked in class today of non-fiction writing and dryness versus non-credibility. It's a fine line one must tread.
The characters one writes get better through time too. The more we're around people, the more we understand humanity, and once we understand humanity a little better than the moment before, our characters will reflect that in our writing.
Plots are something that is secondary to characterization in my opinion. I read for characters, isn't that why we all read? Otherwise, a plot summary would be just as good as the real thing, wouldn't it?
Anyway, just some things to chew on.