My point was mainly that leagues are leaning towards computer-accurate stuff because mistakes are increasingly easy to spot.

Arguing about calls when we were watching blurry slow-mo on CRTs isn't the same as when we're watching crystal clear 4K.

Even with a challenge system as you describe, you still have potential for an ump missing calls that are obvious to everyone watching on TV.

Being able to challenge is good, sure, as a bare minimum, but it's very arguable that players shouldn't have to.