You really don't understand the way the NFL is structured, do you? In the vast majority of games, the better team is favored by a touchdown or less. Since you seem to struggle with that concept, what it means is that, despite what you seem to think, teams are pretty evenly matched throughout the league. That creates lots of 4th quarter ties, and a 4th quarter tie is not an indictment of a QB as you're trying to indicate in your uninformed post. That's why a QB's 4th quarter performance is a key stat and not a throwaway number like so many others.
In other words, 4th quarter performance is a key indicator of whether a team's QB is really THE guy you want behind center. It usually correlates with wins and losses. That's why Dak is the winningest QB in the NFC and second most in the NFL since he joined the league.
You want to measure succes by playoff and SB wins? That's fine, but teams have to get there first.
Something tells me that you think the Bills of the early 90's were terrible because they couldn't win a SB, or that Jim Kelly wasn't 'clutch'. You're a fool.