You asked about the success of the team. Success in the NFL is defined by two things:
1) Revenue
2) Super Bowl Championships
Since Jerry has been in charge of the Cowboys, only two teams have won as many Super Bowls as the Dallas Cowboys (1993,1994, and 1996), they are San Francisco (1989,1990, and 1995) and New England (2002,2004, and 2005). I am being generous to San Francisco since Jones technically purchased the team after Super Bowl XXIII.
Dallas is 163-144 (including the playoffs); 3 Super Bowls with 12 playoff wins. Out of 18 seasons, they have had 10 winning seasons.
Relative to other teams, that appears to be successful.
Believe what you want to believe. It's your team. Just don't be surprised when those Super Bowls keep eluding you.