Not to mention its very dangerous for a pitcher because the ball would be coming at them even faster making it even harder to react to a a line drive aimed at their head.The MLB hasn't switched from wooden bats because the performance of aluminum/composite bats is so similar to wood, they're using them BECAUSE the performance is so much better than wooden bats. At bats in the MLB that result in either a home run or a strike out are becoming increasingly more common. 'Small ball' (manufacturing runs through singles, bunting, etc) is becoming less and less relevant as the game goes on. So if they suddenly let the players use aluminum or composite bats, they'd have to change the name to home run derby instead of baseball because home run numbers would spike dramatically.
All this to say that using the MLB as an example of a sport that hasn't evolved similar to what poolscholar said is flat out wrong and based on a complete lack of understanding on why they use the equipment they use.