One reason outfielders don't have stronger arms might be they don't practice as much as we did. Most teams today don't take outfield practice. Another reason is baseball has to compete with other sports now - basketball football soccer - for the better athletes that might have more skills and stronger arms.
The phrase 'off with the crack of the bat' while romantic is really meaningless since the outfielder should be in motion long before he hears the sound of the ball meeting the bat.
The best plan now is to have as many bosses as possible. I call it boss diversity. If you work for a company and you have one boss and that boss doesn't like you or wants to get rid of you you're in trouble. But if you work for yourself you have lots of bosses who are your customers and if a few of them decide they don't like you that's okay.