Try to think logically and recall history correctly wrote:
Montana was at the very end of his career when he went to Kansas City and he still turned that franchise around and brought them to the brink of a Super Bowl appearance. The 49er's owner Eddie DeBartolo didn't want Montana to get hurt worse which is why the Niners didn't sign him. Montana played in an era where defenders could legally tee-off on quarterbacks. Montana absorbed over 1000 times the punishment Brady has received. Indeed, the modern era of pansy quarterbacks started with the "Brady Rule".
The "Brady Rule" prevents a defender on the ground from lunging or thrusting at the QB's knees, i.e., a "cheap shot" at the QB's knees. That's how Brady's ACL & MCL was torn in 08. So, what's wrong with a rule that penalizes cheap shots? And Brady has been playing on a high level on that reconstructed ACL going on 9 years now. Montana has never had a knee injury of that magnitude.
And I wouldn't call this an era of "pansy" QBs, but an era of QBs dropping like flies from bigger, faster & more freakish defenders than from Montana's era. More QBs in the last 12 yrs have gone down to season ending injuries or significant time loss compared to any other time period. There's HOF Peyton Manning's serious neck injury and the 2015 SB year where he missed half the season and limped through the playoffs. This year alone starting QBs have dropped like flies, e.g., Rogers, Tannehill, Palmer, Cutler, Watson, Lynch, Bradford, Winston, Luck (never even got of the blocks for this season). Given Brady's age, playing time and the reconstructed ACL, it's nothing short of remarkable how well he still performs (and he's been clocked some good ones this year).
https://fivethirtyeight.com/features/is-this-the-worst-year-for-quarterback-injuries/