One possible reason could be that his newfound 'godlike' powers make his family feel estranged. They might not understand his sudden transformation and the magnitude of his power, which creates a sense of fear or discomfort, leading them to ignore him.
In this kind of fanfiction, Naruto may also feel a great deal of sadness and confusion at first. However, as time goes on, he could use that pain as motivation. He might think that if his family won't recognize him, he'll make a name for himself in the ninja world in a way that they can't ignore. He could start taking on dangerous missions, not just for the village but also to show his family what they're missing out on.
In the fanfiction, there could be a family curse or some sort of obligation that forces his family to keep their distance from Naruto. They might believe that by ignoring him, they are protecting him or the family as a whole. For instance, if there is a dark force targeting Naruto, they might think that acting as if they don't care will keep him safe from that threat.
As time goes on, Naruto could become angry. He might feel betrayed by his family's lack of attention. This anger could fuel his determination to become stronger on his own, without relying on his family. He may start to train harder and focus on achieving his own goals, using the rejection as motivation.
In such a scenario, Naruto might initially feel sad and confused. But being Naruto, he could try to prove himself. He would focus on his ninja training even more, aiming to show his family that he is worthy of their attention through his strength and achievements.
Dark Naruto might become more rebellious. He could start to distance himself further from his family and focus on building his own power. Maybe he'll find allies outside of his family who understand and support him.
Naruto might initially feel sad and confused. He could try to prove himself to his friends by working hard on his ninja skills. For example, he might train extra hours to show his friends that he is worthy of their attention.
Another reason could be jealousy. If Dark Naruto has certain unique abilities or powers that set him apart from the rest of the family, they may be jealous and rather than embrace him, they choose to ignore him. This would be a rather petty reason, but in the complex world of fanfiction, it's a possibility.
One possible reason could be jealousy within the family. If Naruto is getting a lot of attention from others in the harem aspect, his family might feel jealous or threatened. They could then choose to ignore him as a way of expressing their discomfort.