3 pt stance is over rated unless you are in short yardage. It helps to keep the pads low and drive forward.
Coaching today, especially in the high-school and college ranks is far superior to yesteryear.
The issue is over use, of muscles, ligaments and games played. Some ligaments can't handle the muscle size and you get soft tissue injuries; hamstrings, the cl family of the knee, even the achilles.
Yes, strength and conditoning has come a long way, shoot, Gatorade wasn't even invented when I played, we used water and oranges. We lifted, stretched, then ran 1 mile before practice, then went full tilt in practice. Ice bath after practice.
Today, most of that is taken away, changed, thought cruel.