I've never bought into the idea that the talent is watered down because of expansion or anything else. If there are so many pitchers who aren't ML material right now compared to any era with 16 teams why has the overall batting average been nearly the same since 1940? And lower quality hitters can't be blamed, if they're hitting so often against bad pitchers
http://www.baseball-almanac.com/hitting/hibavg4.shtml
I also don't buy that todays players are that much stronger. The weight training as built up some impressive strength, and homers are up. But many old time players built up strength through off season jobs that involved a lot of manual labor.
Stuff like farming - try slinging 100 Lb feed sacks all day sometime.
Or other jobs. Not prewar, but Aaron supposedly worked on an ice truck. I'm sure I could find a bunch of very physically demanding jobs checking prewar players.
And the point about how long a ball stayed in the game is a good one. Ruth hit 60 hitting dirty mushballs. How many would he hit hitting clean new tight ones?
Foxx hit some very long homers too, some of them haven't ben matched by the steroid crowd. Deep upper deck at yankee stadium, one of 3 fully out of Fenway to the right of the flagpole... The others were Mantle and Rice. (Nomar would have had #4, but they added a bit of wall that's now gone)
So weaker? I don't think so.
And no ammount of training will help make a good hitter. Unlike another poster I'm a terrible hitter. Never faced a real curve, but I did try a 90mph + batting cage. I was very happy to get one audible foul tip out of 60 pitches. And I'm pretty sure there's not much I could have done to improve a whole lot.
Steve B