The old timers played when players where not nearly as big and fast, and they tended to tackle in the proper manner, wrapping up the runner with their arms, instead of launching into them.
Butkus used to try to rip QBs and RBs arms out of their sockets. Deacon Jones used to put a cast on his arm and then slam it against O-linemens' heads. Art Tatum used to try to decapitate receivers. What era are you referring to, the 1920s?