In an interview with Collider, Langford explained how she had made her peace with being cut from such an important storyline.
And I didn’t feel that way at all and the [directors] Russo brothers didn’t feel that way at all.”
As it turns out, the answer was provided in the shape of Katherine Langford, who, in a deleted scene in Avengers: Endgame, was revealed to be Tony’s grown-up daughter and the heir to his legacy.
You don’t want to be in something and then be the sore thumb that sticks out.