They haven’t won anything since the salary cap and neither has the brilliant Jimmy Johnson.
This is true. Most of that lies with Jerry Jones and his insistence on being a GM (and now through his son). Jerry always wants to make a splash and wants to keep his superstar players and will overpay them to keep them in place. That usually means you don't get the 50-53 players on your active roster who are specialists and special teams players but you also feel confident can contribute on offense or defense if called upon. Of course you have to have "team guys" vs "me" guys and it's pretty apparent Dak, Zeke, etc. are "me" guys. I don't think Aikman, Emmitt, or Irvin were "me" guys but I don't think Jerry was going to risk that.
Jimmy's problem was not being given enough time to rebuild teams. I think he could have won with the Dolphins. I think it's the same problem with the Browns right now. Everyone wants immediate results. The Browns org was such a disaster for so long, it's not going to be an overnight thing. I think they can win with Baker and the pieces they're putting around him but they do need a good solid coach. But it takes time and if you're going to jettison the HC or any assistants each year, it's going to disrupt the continuity and what has been built.