This, 1000x. Look at who McNabb had (or rather, who he DIDN'T have) to work with. Really, people expected him to drag them to a Super Bowl with James Thrash, Todd Pinkston, and Freddie Mitchell? Yeah, he got there with TO, but people always seem to forget he didn't have TO for the playoffs until the Super Bowl, so once again he was doing it on his own (well, with the help of a good defense and Brian Westbrook in his prime).
It's the common refrain that I know Joe Namath says all the time, "Quarterbacks get too much credit for wins, and too much blame for losses." Absolutely the truth.