The 'fox god trains naruto' concept in fanfiction typically helps Naruto grow in multiple aspects. He may become more mature as he has to endure the strict training of the fox god. His relationships with other characters can also change. For instance, his teammates might be in awe of his newfound abilities. Moreover, Naruto could gain a new sense of purpose as he discovers more about his connection to the fox god and the ninja world's history through the training.
It often makes Naruto more powerful. The fox god's training gives Naruto new skills and abilities, like advanced chakra control or unique jutsu. This changes how he approaches battles and challenges in the story.