I think people's frustration is that in the two biggest games of the year (NYG & Wash), the Cowboys were outscored 38-0 in the first half of those games. They looked pathetic and were not even competitive. Two huge games with the playoffs on the line and you come out and play like that in the 1st half. That's embarassing and there is no excuse for it. Overall, their record may fall in line with what a lot of people predicted before the year, but they have collapsed in the 2nd half of the season. How many people thought this team would miss the playoffs after starting 7-3, not many I bet. I don't see how anybody wouldn't be disappointed.
As far as the future, I don't really have the warm and fuzzies about the offense. Bledsoe, Keyshawn, Glenn, Allen, Rivera and Adams aren't getting any younger. The offense is old and slow. Bledsoe will almost assuredly be back next year as the starter, but this team still has no long-term solution at QB and until that's fixed, they're not going anywhere.