It's just how the game has changed. In the NFL right now, teams are passing the ball more and more, which is "inflating" the stats of the QBs and WRs when compared to players from the 60s, 70s, 80s, etc.
And to the guy who said Joe Montana didn't have the luxury of "throwing the ball away", he DID have the luxury of the West Coast Offense, which was a revolutionary Offense under Bill Walsh.
It's like how Mike Vick was so good when he first came into the NFL. This is a guy unlike any other we'd seen before in the NFL; the arm of a QB, and the speed of a lightning fast RB? It took teams a good while to figure Mike Vick out.