It could be that the fanfiction writer has a different vision for Harry's future. They might think that Harry's journey would be more interesting if he remained single or formed a platonic relationship with Ginny instead of a romantic one. This can allow for more focus on his adventures and personal growth outside of a traditional marriage.
In some fanfictions, Harry might not marry Ginny because the author wants to explore alternative storylines. Maybe they want to pair Harry with someone else to create new romantic dynamics. For example, they could pair Harry with a new character to show how his character develops in a different relationship.
In some fanfictions, there could be external forces that keep Harry and Ginny apart. For example, a powerful dark wizard might cast a spell that makes it impossible for them to be together romantically. Or the wizarding society in the fanfiction could have new rules or social norms that oppose their union, causing Harry not to marry Ginny.
In some fanfictions, Harry might not want to marry Ginny because he may still be haunted by his past traumas. For example, his experiences with Voldemort could have left him feeling that he doesn't want to put Ginny in any more danger. He might think that his enemies could target her because of their relationship. Also, he could be focused on his own personal growth and self - discovery, believing that marriage at that time would hold him back from exploring his identity further.
There could be various reasons. Maybe the person Dumbledore wants for Harry doesn't have a good personality or they have different goals and values. Or it could be that Harry simply doesn't feel a connection with that person.
Maybe in the fanfic, Harry has some unresolved personal issues. He could be haunted by his past traumas, like the death of his parents and his battles with Voldemort, which make him feel that he's not in the right mental state to get married.
A possible plotline could be that Harry decides to break off his relationship with Ginny before any talk of marriage. This causes a rift in their friend group, with some taking Harry's side and others Ginny's. Another plotline might involve Ginny trying to change Harry's mind by showing him how they could have a great future together, but Harry remains steadfast in his decision not to marry her due to his own insecurities.
Ginny could be heartbroken. She might have expected to marry Harry after all they've been through together. She could initially go into a state of shock and disbelief, not understanding why Harry has refused.
Harry Potter has his own moral compass. Ginny is an important person to him. The idea of slutty Ginny fanfiction is disrespectful to her character. Harry has seen Ginny grow and develop, and he knows her true self. He doesn't want her to be objectified in such a vulgar way in fan - made stories.
Well, perhaps Ginny is obsessed with Harry fanfiction because she has a deep connection to Harry in the original story. Fanfiction allows her to explore different scenarios and relationships that might not have been fully explored in the official books. It could also be that she simply loves the idea of Harry so much that she wants to read all the different interpretations of him in fan - created stories.
In some fanfictions, Ginny might be mad at Harry because of a misunderstanding. For example, she could misinterpret his actions towards another girl as being unfaithful. Maybe he spends a lot of time with Hermione on a project and Ginny thinks there's something more between them.
Perhaps the main antagonists are some of the old - fashioned wizarding council members who believe in arranged marriages for political stability. They force Harry into the marriage with Ginny without considering their feelings, and they would oppose any attempts by Harry and Ginny to break free from the forced union.