Players are as tough now as they have ever been.
They are stronger, faster and more athletic. They take way more stress on their body than they did in the 50's and 60's. It's not even close.
The problem is that as they get better in terms of speed and strength there is no way you can strengthen an ACL like you can a muscle.
So if you have people who are much heavier, stronger and faster hitting you than in years gone by it doesn't matter how strong you are it won't help your acl or achilles.
Softness is mainly a mental condition and these guys ain't soft.
There is nothing either good or bad, but thinking makes it so.