Aside from Murray the other players were already past their prime and in decline.
I agree. He's paid plenty of players big bucks and then seen their performance (or behavior) plummet. Aikman, Irvin, TO, Austin, Johnston, Sanders, Barber, Bryant, Romo, arguably Ware. We overpaid for all of these guys on their last contract. Those are just the most obvious examples. I do think Jerry and Stephen have learned and are getting more astute. Their outstanding drafting is also really helping things. However, we are going to have to start consider trading some of our good players at some point. We are going get back in salary cap hell soon with a less than SB-caliber roster.
Also, I do think if Dak doesn't really improve we're going to going to be a perennial also-ran. I just don't see teams with average QBs advance to the show anymore. I do like Dak a lot. He's just not an elite passer. Elite leader. Excellent decision maker. Very good runner. Tougher than nails. Just not a pinpoint passer.