According to The Art of Marvel Studios’ Avengers: Endgame, the A-Force scene was going to originally include a lot more of a team effort to help Captain Marvel.
The A-Force scene in Avengers: Endgame was originally a lot better.
The scene in question finds Carol Danvers as she arrives on the battle field to help take down Thanos.
Regardless, screenwriters Christopher Markus and Stephen McFeely felt it would have been a missed opportunity had they not gone through with it.