They're not pitchers, they're throwers.
A true MLB pitcher has multiple pitches and accuracy and changes speed, pitches to contact, etc
Today's throwers throw 1 pitch as hard as they can, with 0 accuracy or change of speed, and maybe have a modest breaking ball or cutter
By the 2nd time thru the order, batters are only too happy to swing for the fences.
The ONLY pitch the human eye cannot adapt to is a change up that is 8 mph less than a fastball a pitch prior. The eye cannot detect that change.