Mac, if you had said that to me in person when I was young, I would have been happy to demonstrate what good athlete baseball players can be.
In high school I played varsity baseball and football, I also wrestled, heavy weight (285+) I could run a 40yard dash in just under 5 seconds in full football uniform. Real American football that is. Not run around in circles whining and not using your hands crap. What's up with that; pick up the damn ball and run like a man!
I'll give European soccer players credit; some are good actors. Nobody cries and fakes being hurt after being touched like a European soccer player.
Injuries in high school started the snowball down the hill for me, and I did nothing but inadvertently (stupidly) speed it up. I played semi-pro baseball and football for over 10 years after high school. All the while working 50 to 100 hours a week. I used to say "there will be plenty of time to sleep when I'm dead"
I was raised on homecooked food, with lots of vegetables, I love greens. Choosing to live on burbon, beer, and junk food as a young adult didn't cause my injuries, the injuries came first. That lifestyle caused other problems. Not the least of which was poor choices with woman. "Too many women and too many pills" And all the other things that go with it.
Most of those guys are pitchers. When you can throw a baseball 90+MPH with pinpoint accuracy you can get away with not doing much else. But even most pitchers are great athletes. Nolan Ryan for example. A few are catchers, which require tremendous quickness, dexterity, and the ability to absorb pain.
It's true lifestyle can be a factor, diet and exercise play a part.
When I could no longer play and cleaned up my life I coached. As a coach I focused on the fundamentals of baseball and fitness for my young players. A lot goes on behind the scenes that fans never see.
There are a variety of reasons for knee problems, almost as many as there are people with knee problems. There are no simple solutions to complex problems.