What do you mean by "excuses"? The reason is that the team hasn't been very good. Is "not very good" an excuse? That's the reason most teams don't win championships. In particular, the defense hasn't been (and still isn't) very good, certainly not good enough to win a championship. That we made it as far as we did this year was nigh on a miracle. And Romo's a big part of that miracle.
Romo has been one of our best players, and he was one of our best players today. Was he perfect? No. But he made a bunch of plays, didn't turn it over and certainly appeared to me to put us in position to win at the end (although the refs saw it differently). We fumbled a sure touchdown, missed a field goal, gave them great field position on kickoffs, generated zero pass rush and had perhaps the worst safety play I've ever seen today, but because Romo took a couple questionable sacks, he's the problem?