It's a team sport, but if your quarterback cannot elevate your team, it's a losing team sport, and that's what the Cowboys have had for 29 years of experiments at the position.
A great quarterback can elevate good players to be even better players. They do not need every position around them to be an All-Pro to win.
An average quarterback relies on justifications, excuses, blame and other "it's not me, it's someone else" reasons why they fail year after year.
Every team has it's weak players as there are no perfect teams, so blaming other players, many of which are new faces every few years, is nothing more than a desperate attempt to support a failed player who has been here through all of those players.