Technical issues aside, one of the harder things of the last few months is switching over from derivative fanfiction to original fiction. I know a lot of authors started that way, and some recent authors have barely filed any identifying details of their fanfiction.
Now I think that dishonest, and doesn’t acknowledge or throw any cookies to the writer or people who created any beloved character or world. World-building isn’t easy, and it can be intimidating if you see how big it is and the world is detached from the story. That is the seductive lure of contemporary settings, the normal world doesn’t need as much description. But isn’t that a little timid, to act like nothing fantastic existed before the story began? You can say the old woman is a wizard who is hundreds of years old, but if they act like nothing interesting happened to talk about, it’s hard to believe they are that old.
In fanfic, it’s like training wheels, where setting, past, and some characters are mapped out. You create a new story and new characters. (I don’t think rehashes are nearly as interesting) and hopefully you add new stories to the foundation. Basically, all Sherlock Holmes stories not by Doyle are fanfiction. Some tweak things, some even add steampunk or bring him to today, but that important core must be present to be a Holmes story.
As a new writer, you play in those sandboxes, trying to do something new, something true to the original canon, and something others will like. Eventually you want something more than putting your hard work into the ether. Fanfiction at its best gets you fast ego-boost. Original is more hard work, but also gives you the chance of half a cheese sandwich.