AB was out of the league because he was crazy, not because of his talent. He was on pace for 1300 yards his final season 3 years later. Roethlisberger's accuracy and ability/willingness to break tackles in the pocket had been declining for years. It's pretty evident if you go back and watch the games. He was missing easy throws in the playoff game vs Jacksonville, the only reason they scored so much was due to amazing efforts from their skill players.
Roethlisberger's numbers were extraordinarily bad in 2019 even before blowing out his elbow, like at the bottom of the league bad.