1
Players who don't hit the ball over the wall, the smaller guys, get a GOOD amount of extra runs from motoring around the bases. Little guys and big guys have been in balance since the days of Ruth.
Big guys playing the outfield make up for a lot of defense lost by footspeed ... when they throw runners out on the bases.
60 feet was just about the perfect distance to set, as was 90 feet on the bases. If the bases were 85 feet or 95 feet, the entire game would morph widely out of its current ballet symphony.
I don't think that the game just seems to be in balance because we're used to it. I think the guys who set the game up to start with, had a great feel for a balanced fight between the fielders and the hitters... lucky for us...