Recently, Stephen McFeely, co-writer of "Avengers: Endgame," revealed in a Q&A session following a special screening that the writers had considered having Hawkeye sacrifice himself on Vormir instead of Black Widow. In the film, one of them must give their life to obtain the Soul Stone; ultimately, it was Natasha who made the sacrifice.
McFeely stated that removing a major female character from the Marvel Cinematic Universe was no small matter, so the writers considered a version where Hawkeye made the sacrifice instead. He recalled that female colleagues objected to giving this heroic moment to Hawkeye, which influenced the final decision.
Discussing why Natasha became the one to sacrifice herself, McFeely mentioned that she had always been trying to make up for her past actions and came to view the Avengers as her new family after joining them. Clint Barton (Hawkeye), on the other hand, already had his own family. The decision for Natasha to sacrifice herself to save those she considered family was based on this character motivation.
The screenwriters were concerned that the plot was moving too quickly, making it difficult for the audience to fully process Natasha's death. Therefore, they added dialogue at the end where the characters acknowledge the sacrifices made by both her and Iron Man.