He said it's hitting a round ball with a round bat squarely, and I entirely agree it's a really tough skill to master.

But my candidate for toughest skill is pitching.  Why?

     Because a starter normally has to face 30 or more batters, but a hitter only goes to the plate on average 4 times a game. 

     Because a pitcher is throwing at a very small target over 60 feet away, throwing almost as hard as he can, knowing he has to hit the corners of the plate with a strike zone that seems to get smaller and smaller, and having to throw--at least for a starter--at three three different pitches well.

     Because pitching is so strenuous the best starters only go one game in five and usually no more than 7 innings and nor more than 110 or 120 pitches. 

     Because really good starters, despite only pitching one day in five, can demand $20M/year salaries. 

     Because MLB clubs on average have 12 pitchers on their active rosters and 13 other players to cover the infield, outfield, catching, DH, and subs.  If pitching were anywhere near as easy as hitting, clubs would have 5 or 6 pitchers, and the rest position players, who would allow managers to pinch hit more, make more defensive substitutions, use pinch runners more, stack lineups with all righties or all lefties, etc. 

     Because pitching is so strenuous can damage the arm, shoulder, or elbow of the pitcher, but swinging the bat rarely leads to a hitting injury.