He would have met the adversity of a 9-7 2016 Broncos situation much better than a 9-7 2016 Texans situation? I don't know. He sucked in 2015, he sucked in 2016, he sucked in 2017. He just sucked. His one good game was his first start as a fourth year player in 2015 when Hillman and CJ rushed for 170 on 36 carries, then he bumped along at ~60-90 QB rating the rest of his career. He's never done squat.
I don't see any evidence that he would have been useful in this revisionist history mode except for the coincidence that he was on the Broncos roster in 2015.
I'm glad he was a warm body on the roster who won a few games, but he was never any good. You put any other backup QB and you get the same result. Siemian playing in 2015 might have been an upgrade over Brock.