Stafford was 0-3 in the post-season during his decade+ long career with the Lions. He is currently 5-2 post-season (including a Super Bowl championship) in his four years with the Rams.
Jameis had one winning season in Tampa (where he got benched for Ryan Fitzpatrick) and had a losing record here under Dennis Allen, but how many would argue that he would have led the Saints to the playoffs that 2021 year under the reins of Sean Payton had he (Winston) not gotten injured?
Coaches, coordinators, teammates, and the general quality of the organization can absolutely matter and show up in ways if not directly in the box scores.