Dude. Brock Purdy started the Super Bowl last year. And he almost won it. There are many ways to go deep in the playoffs. But, yes, a dynamic QB is the easiest way, but mediocre QBs will continue to occasionally win Super Bowls with the right team around them. And they will often go deep in the playoffs just like they always have on occasion.
People's view of this is skewed because Brady and Mahomes have won so many recently.