Really? You know that for a fact? I would argue, for starters, that boomers are not the key demographic right now that keeps MLB flourishing. And by flourishing I mean that salaries are out of sight, attendance continues to be very good, and the TV ratings (and mlb.com ratings) are solid as well. If you look at the history of baseball, the key factor for keeping attendance up is scoring runs although making the stadiums nice with good sightlines also helps. For individual teams, of course, winning makes a difference, as does losing.
I would be astounded if a survey were done of fans who go and who don't go to MLB games in person, and the finding was, "I just can't stand those umpires any more. Too many missed calls on balls and strikes. That's why I stopped going to games. It's downright criminal that the owners don't fix this problem."
TV might be another matter, but I doubt it. I think you are on record saying you will stop watching a game if the balls and strikes are called badly, but I think you don't have much company when you do. If bad calls were provably affecting TV ratings, MLB would fix it.
The one thing I might agree on is the possibility that MLB would purify the strike zone--use computers or robots to call balls and strikes-- in order to be able to quickly contract it (make it smaller) if the pitching gets too dominant, which has happened before.