And that IS a fundamental change. With a fixed strike zone, you lose a lot of nuance. You lose pitchers feeling out the zone early in a game, you lose them learning the tendencies of certain umpires to call a game a certain way. You lose the drama building fact that an umpire will make the call of least consequence when it could go either way (as in you don't get that close called strike on 0-2, or the same ball on 3-0). You lose an umpire expanding the zone when it's just time to get the game over with. You lose the skills of a catcher who can frame a pitch.
The umpire at one of my son's baseball games this spring told the coaches before the game that he was going to call wide/tight strikes (two baseball widths past the black, he said) and that he wouldn't be calling high strikes (nothing at the letters or above). So we relayed this info to the players (they're only 10 and mostly not listening anyway, but still...). Then the ump went out and didn't call close wide/tight strikes and did call high strikes.
Granted, this is a youth ump. But the idea that this ump - and by extension, every ump - will have his own strike zone to me is absurd on its face. It's hard enough to call the actual strike zone, let's not start trying to make up our own.
Or think of it this way. The strike zone is the target in baseball. In basketball, the goal (hoop/rim) is the target, in hockey it's the goal, in football it's the endzone and the goal posts. Should some officials in those sports get to decide that today the hoop will be 16 inches diameter instead of 18, that the hockey goal will be 75x45 instead of 72x48, that the goal posts will be 19 feet wide rather than 18.5? Of course not. That would be absurd. It's equally absurd that the baseball target changes from umpire to umpire, inning to inning, and even at-bat to at-bat. Do pitchers and batters really want to have to figure out every day where the strike zone is? Some pitchers have certainly benefited from personalized strike zones. I recall Tom Glavine making a good living getting strikes called 6-12 inches out of the zone. That's great for Tom Glavine, but it's not fair to the batter and it's not good for the game.
"Nuance" and "the human element" of umpiring be damned. I'm more interested in a level playing field and getting the calls right. If the technology is there to do that, I want it to be used.
My son was telling me today he'd been reading a book about the early days of baseball; that umpires used to sit in rocking chairs behind home plate. That's a lovely image, the timeless, pastoral game at its most picturesque. I'm glad they did that back then. I'm equally glad the game has moved on. Time for the game to move on again.