I think that saying he brings "nothing to the table" is a bit harsh. The roster he took over and the roster we have now are very, very different and much better now in my opinion. He has this team battling every week, no matter how awful their record is. Also, it's not like we're getting blown out. 7 of our losses this year have been by one touchdown or less. Surely he brings something to the team.
However, I do agree that it is inexcusable to lose as many games as we have this year, injuries be damned. A better coach might have been able to creatively win us some games. Jason Garrett is not that guy.
How would you feel if the team brought in a new Offensive Coordinator and a new scheme and left Garrett to being a talent finder and motivator type HC? I think if Garrett was willing to give up his outdated scheme in favor of one that is more dynamic and creative, we would see a lot more success.