Of course it's not just the QB.
You need the GM to build the team -- but sometimes the team doesn't get over the hump (like all those Chargers teams earlier in Rivers career)
You need the coach -- and not just a regular season coach, but a coach who can win the critical game, unlike Reid, Levy, Shotty, that idiot who blew the SB for Atlanta, etc.
And you need the QB.
So yeah, you need a lot to go right and it can still be derailed in a single elimination playoff tournament. On the other hand, if you have a decent team, QB and defense, you can get hot for a month and win a championship (Giants).