Yeah I wouldn't agree with it but I'd at least understand the system QB argument if he put up mediocre stats like other "system QBs" such as Montana (or Manning when he threw 3 touchdowns and 7 interceptions during his first "superbowl run"
), but he's top 4 all time in career passing yards, passing touchdowns, passer rating, and he's done it only throwing interceptions on 1.8% of his pass attempts. Of all the other QBs who are near the top in purely quan ative stats like career passing TDs, the next best in terms of interception % is Drew Brees at 2.4%. There's no reasonable argument that Brady's career statistic, both quan ative and qualitative, aren't among the best.
The "system" works because of how patient Brady is in taking what's given to him and executing it. You couldn't run the 8 minute, 15 play drive that they opened up with against the Chiefs with Aaron Rodgers, Favre or Peyton Manning. Rodgers or Favre would have fallen behind on downs at some point by chucking an unnecessary 40 yard heroball pass instead of taking the 5-7 yard checkdown that was wide open, and Manning would have ed it up by audibling out of the running plays that were gashing KC and going one dimensional. If the goal is winning games then comparing which QBs are best at playing heroball is a stupid way to look at it.