It was a dumb thing to say when he had the best team in the league. It would be an idiotic comment for any general manager to say out loud.
At that time, his 1 out of 500 coaches, Barry Switzer, did not get the team to Super Bowl XXIX. If not for the players, his 1/500 coach would not have been able to scream 'WE DID IT OUR WAY!' after winning Super Bowl XXX.
Football is a sport that depends on the right combination of coaching and players to sustain success. Jimmy Johnson was the right coach. Jones divorced himself from the right coach WHEN his franchise was on top of the world.
Dismissing his irrational statement for how he could win without Johnson is not taking into account his mentality. Jerry Jones did not mysteriously morph into an incompetent buffoon concerning football management in just the past 30 years. He has always been one.