Can fan fiction writing help a writer become one day a writer of their own original fiction? Most fan fiction writers will never go beyond the fan fiction. Admittedly, a lot of it is not even well written. But the stories are for the fans' own interests, and that’s okay. But there are those who will one day take the step past fan fiction and delve into their own worlds. Look what happened to Fifty Shades of Gray. Though in my opinion, that is not the best example, just one that came to mind.
I was one of these once upon a time, though I was writing my own works long before I started into fan fiction. But fan fiction has enabled me to keep writing, put words to paper and later, online. It made me think like the screenwriter of the series or movies that I liked, by getting into their head, and hopefully wrote their characters and story the way they did. Yes, I did add some of my own original characters. But the fan fiction kept me writing until I felt ready to open the door to writing my own fiction and submit them.
So writers, if you get stuck on your own work in progress and want to write something that day, try a short story about your favorite TV show or movie. It doesn’t hurt, it’ll be a mini vacation from the writer's block that stymied your own work, and you will be doing some form of writing. And hopefully doing this will enable you to get back to your manuscript.