Fair/foul calls are the epitome of OBJECTIVE calls. There's nothing judgmental/subjective about fair/foul. The ball is on one side of the line or the other. period. Football: The guy either caught it, or didn't. He either had 2 feet in or didn't.
Then every call in baseball and football should no longer be reviewable. The umpires mentioned the idea of allowing the staff on the field to overturn fair/foul type of calls which are the epitomy of judgement calls that could be reviewed. If staff on the field could have seen the video and compared it to the rule itself, it would be overturned.
infield fly rule: the ump has to make a decision based on the situation and how the players are interacting with one another to see whether or not to call something. There's no magic line in the outfield that controls the IFF, hence it was JUDGMENTAL/SUBJECTIVE. There's a huge difference. Just like you can't review holding calls or anything in football that's just the ref's opinion on a play.