I loved Johnson, but I find it telling that he had no success anywhere but in Dallas.
My point is it's never one guy.
He had one stop in the NFL beyond Dallas - Miami. And yes, he didn't win a SB there but he had a winning record there. He made the playoffs in 3 of his 4 years there and also had 2 playoff wins in 4 seasons there (compared to our current coach who has 2 playoff wins in 8 years). Not great but hardly poor. So it's not like he had 5 NFL stops and all were bad and only Dallas was a good run.
He was a very good at The U, granted that's college.
On the flipside, you have Jones who has gone through half a dozen coaches since Johnson left - one won a SB with the team Johnson and Jerry built and the others pretty much were blah.
I think the evidence is there that while the Cowboys of the 90s were a co-effort between the two, Johnson probably had more influence on how those teams were built than Jerry. Again that's not to say Jerry gets zero credit here. Shoot, he hired Jimmy so he gets a ton of credit for that.
But if Jerry was such an influence on those teams and so good at roster building as evidenced by those 90s teams, then why has he gone 23 years with basically zero success as GM?