In the fanfiction, Naruto might neglect his heritage because he has a different goal in mind that he believes is more important. He could be so focused on achieving peace in a different way, like through uniting different groups without emphasizing heritage. He might also be afraid of the responsibilities that come with his heritage. If his heritage comes with a lot of power and leadership roles, he could be hesitant to take them on and thus choose to neglect it in order to avoid those burdens.
Maybe he's been influenced by someone who has a different view of heritage. For example, if he meets a character who believes that one should create their own identity rather than relying on heritage, Naruto could be swayed. Another possibility is that he has some sort of resentment towards his heritage. Perhaps there are things in his family's past or in the traditions associated with his heritage that he doesn't agree with or is ashamed of.
Naruto's neglect of his heritage can have a profound impact on the overarching theme of the fanfiction. If heritage represents a sense of identity and purpose in the Naruto universe, his neglect means he's sort of adrift. This can change the story from a typical 'coming - of - age - with - heritage' type to a more 'finding - oneself - despite - neglecting - heritage' plot. It could also lead to new character developments as he encounters different cultures or powers that make him reevaluate his decision to neglect his heritage.
One possible reason could be the burden that comes with his heritage. Naruto's heritage is filled with great power and responsibility. Maybe he feels that he can't live up to the expectations of his clan or predecessors, so he rejects it.
It could also be due to some family curse or prophecy. In the Naruto universe, there are often strange powers and curses. Maybe there was a prophecy that said Naruto's family had to keep their distance from him to protect him from some greater evil. So, they chose to neglect him in order to keep him safe, even if it was a difficult choice.
One reason could be that his siblings have some special abilities or talents that overshadow Naruto. In the ninja world, those with unique powers often get more attention. So, if his siblings possess something extraordinary, Naruto might be pushed to the side.
One possible reason could be that they are too involved in their own shinobi duties. The world of ninjas is full of dangerous missions, and they might be constantly away on important tasks, leaving Naruto feeling neglected.
One possible plot twist could be that his heritage is linked to an enemy he thought was unrelated. So he has to reevaluate his views on the whole conflict.
Maybe there are secrets in the family. For example, his parents might be involved in some dangerous and secretive missions that require them to keep their distance from Naruto to protect him, but Naruto misinterprets it as neglect.
One possible reason could be jealousy. If Naruto has the rare Mokuton ability, his family might be jealous of his potential power and neglect him out of spite.
One possible reason could be that they are too focused on their own problems or duties. Maybe they are involved in some important shinobi business that takes up all their time and attention, causing them to overlook Naruto.
Perhaps he's been influenced by someone who gives him bad advice. For example, if someone tells him that natural talent is enough and training is overrated. Also, he could be dealing with some personal problems, like a conflict within his family or among his friends that takes up all his time and mental energy, causing him to neglect training.