SYSTEMS make the skill players in the NFL.
QBs, WRs, even RBs to some extent.
The Patriots have an outstanding system.
The Packers have an outstanding system.
The 49ers of old (and new it seems too) had an outstanding system.
That is how you get dynasties. That is how you get back to back HoF caliber QBs. That is how you get WR cores that it doesn't seem to matter who is out running the patterns, they all put up pro-bowl numbers.
Brady is a great quarterback. Favre was a great QB. Rodgers is a great QB. Montana was a great QB. Young was a great QB. But it's their SYSTEMS that they played in that made them some of the greatest of all time.