One thing you learn from studying baseball history is that people have always predicted the sport’s demise. Over and over, the game weathers every perceived crisis and continues to thrive. More than 70 million fans will attend major league games this season; another 40 million or so will go to minor league games. Countless more watch the sport on television and online. And yet attendance is down, and more and more balls are being kept out of play. Some longtime observers consider the shifting landscape — hitters swinging for the fences, pitchers throwing everything with maximum effort, fielders standing in...