The Bengals wrecked the league with Browning for 7 or so games last year. The Chiefs still found major success with Henne when Mahomes was injured, once or twice even in playoffs. Payton still went 9-8 with Drew Brees missing many, many, many games.
All the teams you listed with the exception of the Dolphins have coaching issues, the Saints just being the worst. The scenarios I listed all have good coaches.
The difference, coaching.