The author should work on improving the writing quality. This could involve getting an editor, studying good writing techniques, and practicing. Use more vivid language to describe the settings and emotions, making the readers feel more connected to the story.
Developing the characters more fully would help. Give them multiple layers of personality, backstories, and let them grow and change. Let the protagonist have internal conflicts other than just external battles.
Firstly, the author could focus on creating a more unique plot. Steer away from the common tropes and come up with something fresh. For example, instead of the typical fantasy setting, set it in a post - apocalyptic world with a mix of magic and technology.