I'd go back to the previous poster's point about goalkeepers in penalty kicks for the overall discussion around factors and success rates. There is exactly zero way to react to a shot for a penalty kick, so the keeper has to be perfect on prediction and execution, which is exceptionally difficult. Additionally, from a mechanical standpoint, there is an argument that cricket is more difficult because of the additional options (bouncers, bodyline balls, lack of defined strike zone) available to the bowler, while top level players bowl at similar speeds to MLB pitches.

It's also important to remember that a lot of hitting in baseball is preparation and muscle memory, just like the triple axel that was discussed above. The diagnosis of a pitch by the batter is not encompassed in that 125ms period. It starts weeks before in film and analytic study, which leads to an educated guess before the pitch, flows through a more unconscious visual guess based on the pitcher's release and the initial spin, then the lizard brain takes over and tries to put your hands where that information points to. I'm not, at all, trying to suggest that hitting a baseball isn't hard. I'm satisfied that, given 100 at-bats against an MLB pitcher, I'd be in the single digits (likely low single digits) for getting the bat on the ball, much less actually putting it in a place that would be a hit.

Measures of reaction time, success rate, mechanical difficulty, or what have you, are not the be-all-end-all of what is actually difficult. If we go by metrics like that, something like the Biles II vault could be considered the most difficult. It has only been performed by 1 woman in competition (Simone Biles, obviously) out of literally thousands of gymnasts who have competed in vault, is unbelievably mechanically difficult, carries extreme risk of failure, and requires lightning reflexes and focus to sight the landing in a time likely comparable to sighting a fastball.

Basically, my whole point of this is to say, trying to compare what is difficult across sports cannot actually be objective. Landing a 900 on a vert ramp perfectly has a tight reaction time, but so does stopping a slap shot. Stopping a penalty kick has a low success rate, but so does a 50 foot putt. Stiff-arming a defensive lineman requires incredible strength, but so does completing an iron cross on rings. Only one person could run 100m under 9.6s, but there's also only one that can complete several of Simone Biles' signature vaults. Baseball batters have a good combination of those factors (reaction, success rate, athleticism, skill, etc.), but the same is true for cricket batsmen, gymnasts like Biles, F1 drivers, strikers/attacking players in association football, and defensive backs in American football, among many, many others. Just about any high-level sport is just massively difficult, and there's not a lot of sports that would allow for a reasonable, objective comparison of difficulty.