Maybe in some fanfictions, Ron is portrayed in a way that doesn't match Hermione's idea of him. For example, he might be made overly clumsy or insensitive, which could annoy Hermione.
In some fanfictions, the relationship between Ron and Hermione might be forced into a very cheesy or unrealistic dynamic. Hermione, being a strong - willed character, would likely be fed up with such a false representation of their relationship.
Another reason could be that the fanfiction is full of clichés when it comes to their relationship. It always follows the same tired plotlines, and Hermione, being the intelligent and forward - thinking witch she is, is tired of seeing such unoriginal takes on their relationship.
Sometimes, the plotlines in fanfiction can be a bit outlandish. If Ron is constantly getting into trouble in a way that Hermione has to constantly clean up after him, it would be understandable for her to be fed up. This could be different from the more equal partnership they had in the original series.
Well, they could ask for Hermione's input! Just kidding. Seriously though, writers could break free from the traditional molds of how Hermione and Ron are portrayed in fanfiction. Explore different timelines or scenarios where their relationship isn't the main focus but still an important part of the story. Also, get rid of any misogynistic or one - dimensional portrayals of Hermione in the fanfics.
Maybe it's a plot twist to add drama and unexpectedness.
Maybe it's because he has deep, unexpressed feelings for Hermione in the original story. Fanfiction allows him to be in different scenarios with her that he might have secretly desired in the real plot.
Maybe he's fed up because the fanfiction often misrepresents the Order's values or actions. In some fanfictions, the Order might be depicted in a way that doesn't align with how he knows them, which could be frustrating.
In some fanfictions, Hermione might be portrayed as hating Ron to create a new and different plot dynamic. Maybe the author wants to explore an alternative relationship path for Hermione, or they could be trying to add more drama by having her oppose Ron, who she is typically friends or more with in the original series.
Well, it could be for love. In many fanfics, their relationship has been through a lot, and leaving together is a way to start anew, away from the prying eyes and pressures of Hogwarts and the wizarding community.
In some fanfictions, Harry might be angry with Ron and Hermione if he feels they are keeping secrets from him. For example, if they discover something important about Voldemort's plans but don't share it right away, Harry could get angry. He's used to relying on them and when that trust is broken, even if it's a misunderstanding, his anger can flare up.
Well, there are several reasons. Dumbledore is this all - knowing figure in the original series, but in fanfiction, his actions can be seen as manipulative. He might be making decisions for Harry without really considering Harry's feelings or wishes. Also, Dumbledore's grand schemes might not always be in Harry's best interest. Harry might realize this and get fed up. For instance, if Dumbledore is using Harry as a pawn in a bigger battle against Voldemort, Harry would likely be angry when he figures it out. And Dumbledore's failure to prevent certain tragedies, like the death of Sirius, could also be a reason for Harry's disillusionment.