One possible reason could be that he's had a bad experience with the taste. Maybe the ramen was made wrong one day and it left a really bad impression on him.
One possible reason could be that Naruto might feel Kakashi is too strict with his training. Maybe Kakashi's methods are too harsh for Naruto, making him frustrated and gradually developing dislike.
In the original story, Naruto loves ramen. It's a big part of his character. So in this fanfiction, it's a complete opposite. It changes the fundamental aspect of his relationship with food.
One possible reason could be that in the fanfiction, Kakashi might have made a decision during a mission that Naruto strongly disagreed with. For example, Kakashi could have chosen to sacrifice something important to Naruto in order to achieve the overall mission objective.
It could be a fanfiction that focuses on a character in Naruto experiencing withdrawal symptoms related to ramen. Maybe Naruto himself is deprived of his beloved ramen for some reason and the story explores how he copes.
One possible plot could be that a new and mysterious ingredient is discovered in the Naruto world. This ingredient is added to the ramen in the shop, and it gives those who eat it special powers. Naruto and his friends then have to protect the ingredient from villains who want to use it for evil.
One possible plot could be that Naruto discovers a new secret ingredient for his favorite ramen. This ingredient could be a rare herb only found in a hidden part of the forest. He then tries to convince Teuchi, the ramen shop owner, to use it in the ramen. Along the way, he has to face off against some ninjas who also want the herb for their own purposes.
One possible reason could be jealousy. Maybe his brother has some special abilities or gets more attention that Naruto feels he should have. For example, if his brother is really good at a certain jutsu and is always praised for it while Naruto struggles, that could lead to resentment.
Naruto and his son, Boruto, could be main characters. Boruto might not understand his father's love for the ramen shop at first, but as the story progresses, he comes to appreciate it. Another character could be Shikamaru. He might be there to relax and have some ramen while also using his intelligence to solve any problems that arise in the shop, like a sudden shortage of ingredients.
Perhaps a ninja who has a grudge against Naruto because he once ate all the ramen at a festival, leaving none for the ninja. So this ninja decides to target Ichiraku Ramen and tries to put a curse on the ramen that would make anyone who eats it sick. Naruto has to figure out how to break the curse and stop the ninja.
Maybe in this fanfic, the author wants to create a unique and dark plot. Kushina might be made to hate Naruto due to some kind of misunderstanding. For example, she could be misled to believe that Naruto has some connection to a great evil that she is against.