Well, it might be that the fanfiction focuses too much on Sakura in a way that Naruto feels is unfair to the other characters. Naruto is part of a big world with many important people, and if the fanfic just hones in on Sakura all the time, he could get fed up. Also, if the fanfiction has Sakura constantly putting Naruto down or not appreciating his efforts like in the real story, that could be a reason.
Perhaps the fanfiction is full of overly dramatic and unrealistic scenarios involving Sakura. Naruto is used to real - life - like (within the context of the Naruto world) situations. When the fanfic has Sakura in situations that are just too far - fetched, like suddenly having superpowers that don't fit the Naruto universe, Naruto might get tired of it. Also, if the fanfiction changes the dynamics between him and Sakura in a way that goes against his values, such as making Sakura act in a cruel or unjust way towards him, he would surely be fed up.
One reason could be that in some fanfictions, the characters of Team 7 are portrayed out of character. Naruto might be fed up if they make Sasuke too brooding in a way that doesn't seem true to the original. Also, if the fanfiction focuses too much on shipping within Team 7, like Sasuke and Sakura, and ignores Naruto's growth and importance, it could annoy him. Another possibility is if the fanfiction makes the team seem too dysfunctional in a way that doesn't match Naruto's view of his comrades.
Perhaps the fanfiction keeps rehashing the same tired storylines about Konoha. Naruto might be tired of seeing the same things over and over again, like always focusing on the village's dark secrets in a clichéd way instead of exploring new aspects of Konoha and its people.
One reason could be the lack of recognition he gets in the village despite his great contributions. In the fanfiction, Naruto might feel that his efforts to protect the village are taken for granted.
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.
It could lead to a shift in the type of fanfictions being produced. If Naruto getting fed up with Sakura fanfiction becomes a popular concept, more fanfic writers might avoid writing in that vein or might try to rewrite the relationship in a more acceptable way, which in turn changes the overall landscape of Naruto fanfictions in the fandom.
In some fanfictions, Sakura may make decisions without considering Naruto's opinion. Naruto values his friends and their input, so if Sakura goes ahead and does something like endangering the team or making a big decision on her own that affects everyone, Naruto could get mad. Also, if Sakura were to insult Naruto's dream of becoming Hokage, that would definitely be a reason for his anger as that dream is very important to him.
One possible reason could be that Naruto realizes their goals and values are too different. Naruto is highly focused on protecting the village and achieving peace on a large scale, while Sakura might be more concerned with her medical career and the well - being of a smaller circle. Another reason could be the presence of Hinata. Naruto might gradually develop deeper feelings for Hinata which could lead to the break - up with Sakura.
If Naruto gets fed up with Team 7 fanfiction, some fans who love Naruto's perspective might stop reading those fanfictions. This could lead to a decrease in the popularity of certain types of Team 7 fanfictions. Writers might then have to change their approach to keep their readers.
One possible reason could be that Naruto realizes Sakura's true feelings for Sasuke are unwavering. After many attempts to win her heart, he might come to the conclusion that he's just chasing after someone who will never love him back. So, he decides to give up and focus on other aspects of his life, like his ninja duties or his friendships with other people in the village.
One possible reason could be a misunderstanding. Maybe Sakura makes a decision that Naruto strongly disagrees with regarding the safety of the village or their friends. For example, if Sakura decides to trust an enemy without Naruto's knowledge, Naruto might get so angry that he lashes out at her.