It's not that simple.
Have you heard Peyton Manning, or Tom Brady in a huddle or on the sidelines? An elite QB has more than just his play on the field. He can inspire his teammates to go beyond the level of play that was considered their maximum.
Players that witness greatness in a teammate want to be great as well. They don't want to be the one who held everyone else back, especially their elite QB. They play harder. The elite QB sets the standard for everyone else on the team. Troy Aikman and Roger Staubach was that way.
They aren't exactly carrying the team. However, that team has someone that can demonstrate how to respond in the critical moments of a game. The team would not come close to accomplishing what they did without him.
I heard players say this about many elite quarterbacks, including Roger Staubach. "We feel as though we are never out of a game with _______."
The teams that win in the playoffs are the best teams.. It never changes
Blatantly false. Otherwise, explain a 9-7 wildcard team like the Giants beating a 13-3 team like the Patriots in Super Bowl 46.
I have analyzed several years of NFL football and can tell you that the best team in the regular season wins only about 50% of the championships. They often fall victim to teams quarterbacked by guys like Joe Montana, Aaron Rodgers, Roger Staubach and Patrick Mahomes.