I feel like discussing how the film concludes would diminish its impact and detract from the solid acting on display. The presence of Will Smith as the central figure was essential to the movie’s success; he guided the narrative, convincingly portraying the sense of dread and loneliness present within it. His largely solitary performance effectively conveyed a feeling of intense desperation. The film contains some genuinely heartbreaking scenes, and the tone becomes quite somber throughout its latter portion. Regarding the ending itself, any comments I could offer would likely echo what others have already said. I’m uncertain why they chose to alter it from the book's version, and that alteration prevents the movie from achieving a higher rating.

Source on TMDB