I'm not sure what you mean by calling it "fanfiction." I have hard time generalizing about fanfiction because it can range from awful to fantastic. What does the label "fanfiction" imply to you? What, exactly, about Homecoming reminds you of fanfiction?
To me, the generalised term fanfiction normally means including favourite characters, storylines, sometimes dialogue, obvious references to past events, crossovers and anything that prevents the natural progression of the story and/or characters OR retells a past story for the sake of enjoyment.
I had hoped Janeway and crew would be alone, save for Admiral Paris, Libby and other family characters created in the Voyager universe, and not include characters from other Trek incarnations.
Hmmm. Not sure I can go with your definition here. I'm assuming that the episodes on TV are NOT fanfiction, yet they have many of the elements that you designate as common to that kind of writing, including reusing favorite characters and story lines, obvious references to past events, and crossovers--even retelling for the sake of enjoyment.
Just a few for your consideration: TNG's "The Naked Now," "Sarek," "Unification," and "Relics"; DS9's "Defiant," "Trials and Tribble-ations," and the three episodes with Lwaxana Troi; VOY's "Death Wish," all of the Q episodes, "Fair Trade," and "Flashback." I know there are a lot from ENT, too, but I really am not that familiar with the series.
So, I'm still not clear on what makes "fanfiction" different. Can you clarify?