The problem with both Weeden and Cassel is that they don't have the ability to manipulate a defense. Romo does so much more with his eyes and coverage recognition than is ever seen by the average football fan. He moves safeties with his eyes. He calls out coverages right to the face of a defense (I remember last year him telling the Eagles MLB to "come on up" as he was making his line adjustments. He KNEW the defense they were trying to fool him with).
When you have QBs that lack that ability you are going to have WRs that are "wide open" at some point in the route. The problem is that the reason they are wide open is because the QB is typically past them in his read progression and the QB doesn't have the time in the pocket to get back to them once he's been deemed "covered" early in the play. The reason Romo (and many other top tier QBs) make those throws to these "wide open WRs" is because he's moved the safety off that spot with his eyes and he KNOWS that WR is going to be "wide open" later in the read progression. That's why Romo is the king of extended play heroics. It's also the reason that he's successful in an unimaginative offense that relies solely on flawless execution. Romo does a lot more than just QB this team. He covers a lot of the deficiencies in this organization from top to bottom. He has the entire time he's been the starting QB for this franchise. You need no more proof than the last five weeks.