I agree with Timby that Cassel's not a QB that you can use to carry the team. If you have a good team already put together, Cassel would be a good option, but if you're a mess and need the QB to carry the team and need the QB to win games for you, Cassel's not the guy.
I'm of the opinion that for a team to succeed in today's NFL they MUST HAVE a franchise QB. The Ravens and Dilfer was an anomaly. You have to have that Manning, Brady, Rothelisburger (sp?) or dare I say it, John Elway, to take teams to that high level of competitiveness that ends with a SB victory.
Matt Cassel is not taking any team to the SB. He might win you a lot of games with the right talent around him (see 2008), but a SB? The only way he gets to the SB is either as Brady's backup, or with a ticket to the game.
And as long as the Chiefs stick with him, they ain't going anywhere. Which I guess for you is a good thing.
In general, I would agree with you to a point. When one considers the fact that the league is becoming more and more passing-oriented with the rules and how things are run, and how hard it is to put together absolutely dominant teams with parity and salary caps and players demanding monsterous salaries, a capable QB who can win the games for you is a must. But, if you're lucky enough to put together a defense that can win the game for you or to a lesser degree, a running game that can carry the team, then a great QB is just an added bonus. If you have a good or average defense/ run game, then you need the QB to get you to the next level. But if you have a truly great defense or run game, then you only
need a QB who won't get the team into trouble. A great run game is hard to say that for because it could potentially be easier to stop if the opponents start gearing entirely for the run.
To use an example I'm familiar with, there's the Broncos. For several year (obviously, not the last few), they've had a habit of fielding great defenses that would wear down towards the end. In 2006, we only allowed 4 TD through the first 7 games and we became the first team since the '40s to start the season 11 quarters without allowing a TD. In the first 7, they only allowed more than 10 points once, and that was in a game where Denver turned the ball over 5 times. Even then, the D only allowed 18 points, all in the form of field goals. Things started going downhill after the 7th game, but if the defense had kept that going, I think they could have carried a struggling Plummer a long ways. A dominant enough defense can sometimes be all you need to get through.