Distant Marvels is fiction for sure. It has elements that are beyond what we encounter in the real world, crafted solely for the purpose of creating an engaging story.
Some people might create such fanfiction because they have a different view of the original 'Harry Potter' series. Maybe they don't like the characters, the plot, or the overall world - building. They want to express their dissatisfaction through creating their own stories that go against the general positive perception of 'Harry Potter'.
Well, in some fanfiction, a writer might portray Bill Weasley as 'sucking' perhaps because they want to create a different or more complex character arc for him. Maybe they have a different view of his actions or relationships within the story. It could also be just a creative choice to add drama or conflict.
Maybe the protagonist has a weak personality. For example, being overly indecisive in making choices, which can make the story progress seem dull and frustrating.