Haha fair!
So the reason I said the QB is the biggest weakness is because most plays he does outside of handing the ball of to a runner a kind of high risk/high reward situations. Which means, by law of averages, eventually your QB is going to throw a clanger in a crucial situation; and even more so if the opposing defense is even average, let alone some of the elite ones in the playoffs.
If you look at SB winners, apart from three (P Manning; Brady; Brees), most of the recent teams had quarterbacks who were very early in their career (usually their worst period unless they are the anomalies). And even those guys: Manning at Denver had to have much more restricted style of offense and a dominating defense to win after the more QB-centric offense got eaten alive by Seattle, Brady's early offenses were also very heavily restricted to minimise QB mistakes coupled with dominating defenses. Recently that's changed a bit but I'd say these three are the exception to the rule.
I can't remember how it went for Brees. But my point isn't to say Alex Smith is the pinnacle of quarterbacking or anything: it's really that (1) you don't need a great QB to win at all, and (2) teams are overpaying for QBs in terms of draft picks and contracts when they can afford to get an avg to above avg QB, change their offensive schemes to give the QB fewer reads on passes and even decrease the amount of passing period, then use the rest of that cap space to get a strong team.