Sasuke would likely be conflicted. On one hand, he has his own issues with Konoha, but on the other, he might be surprised that Naruto, who was always so loyal, would give up. He could try to understand Naruto's reasons or maybe even join him depending on the situation.
It could be that Naruto has a vision of a different kind of life or place where he can truly be at peace. He might meet someone from another village or group who shows him an alternative way of living that is more appealing than staying in Konoha. And so, he gives up on Konoha to pursue this new path.
It could also be that he is tired of the false expectations created by fanfiction. In fanfiction, his character might be portrayed in ways that don't match who he really is. He wants to be true to himself and his ninja way, so he gives up fanfiction.
Some fans might be disappointed. Fanfiction often allows them to explore different scenarios with Naruto's character. If he gives it up, it's like closing a door on those creative possibilities.
Perhaps Naruto is fed up with Konoha's fanfiction because he wants a new adventure outside of the village. He has spent most of his life in Konoha and might be craving for a change. He could be bored with the same old politics and power struggles within the village. Also, he may have realized that the ideals of Konoha are not as perfect as they seem, and this disillusionment makes him tired of it.
One possible reason could be that he experiences a great loss, like the death of a dear friend. This might shatter his confidence and make him lose his passion for being a ninja.
One reason could be exhaustion. Naruto has been through a lot in the original story. In a fanfic, if he is continuously put through more and more difficult situations without proper breaks, he might just give up out of sheer tiredness.
Well, in some fanfictions, Naruto might outsmart Konoha by using his unique knowledge of the village's secrets that others don't know. For example, he could use his understanding of the old tunnels under Konoha to his advantage in a situation where he needs to escape or gain an upper hand in a conflict.
Another factor could be the nature of his ninja life. It's full of uncertainties and risks. He may worry that if he falls in love, his loved one could become a target for his enemies. Naruto has made many enemies over the years, and he wouldn't want to put someone he loves in danger, so he decides to give up on love.