Original Iron Man Writers Speak Out On Tony Stark's Fate

Avengers: Endgame was directed by Joe and Anthony Russo, marking their fourth entry into the series.
Yet Endgame was written by Stephen McFeely and Christopher Markus and was their sixth film in the series.
The MCU launched with Iron Man back in 2008, which was written by Art Marcum and Matt Holloway.
So what does the duo think, looking back on Tony Stark's trajectory and the impact of the series?
"It's sad, but it had to be that way.