Marc Webb, the film’s director, explained in an interview with the Los Angeles Times that the decision came down to the complexity of the story. "It was something we only discovered when we were shooting and then in the edit room," Webb said. "It was very difficult to introduce someone as a competing love interest when so much is on the table with Peter and Gwen."
Gwen Stacy, played by Emma Stone, had already become a key character in this version of the Spider-Man story, and introducing Mary Jane would have muddied the emotional core of Peter and Gwen’s relationship. Webb added that the addition of Mary Jane didn’t make sense given the film’s already crowded storyline.
Shailene Woodley agreed, saying in an interview for Divergent promotions, “Mary Jane was in four scenes in the whole film, and it didn’t make sense... introducing such a vital character to the comics in a movie that had so much going on.”
Woodley’s Mary Jane was originally intended to play a bigger role in The Amazing Spider-Man 3, which would have explored her relationship with Peter after the tragic death of Gwen. However, The Amazing Spider-Man 2 was not the box office success Sony hoped for, grossing only $202 million domestically and earning mixed reviews. As a result, The Amazing Spider-Man 3 was canceled, and Mary Jane's potential future in the series remained unfulfilled.
Though fans never saw Mary Jane on-screen, Webb and Woodley both agreed that it was the right call to remove her from the sequel, allowing Gwen’s emotional storyline to take center stage without overshadowing her fate.
Ultimately, the film’s failure led to the end of the franchise and a reboot in the Marvel Cinematic Universe, leaving fans to wonder how things might have been different if The Amazing Spider-Man 3 had been made.