I get what you're saying but I think it has more to do with focus than bad umpiring.
If you've ever volunteered (or worked) to umpire games it's easy to let yourself get distracted for a pitch here and there after so many pitches and miss the actual pitch which forces you to judge the call on where the catcher caught or framed it.
I think ABS has made them more focused, at least early in the season, than they have had to be in the past when behind the plate.
Another reason that is not talked about is how eye quality worsens as people get older.
Since they rotate umpires behind the plate, they should implement a policy that limits which umpires can umpire behind the plate in games based on their age.
They don't have to fire them (which would violate EEOC laws) but they could exclude them from calling balls and strikes and just keep them in the field.