baseball itself isn't hard, BUT being a pitcher is.
1) Pitcher - strike zone/mound-to-home plate distance/speed/spin on pitches - that's why they give them 4 days off.
2) Hockey - doing too much at once, skate, stick, tiny @ss puck, hitting
3) Basketball - at its essence, almost same skills as hockey, of course of the years people have been able to compensate with athleticism over skill
4) Tennis - is skilled but it's only because you add the racket. Other than that, we've all played handball.
The rest of baseball isn't hard. There's too much idle time playing the outfield so you are simply running down scenarios in your head, over and over again
Boxing isn't hard. Different people have different styles, some have quick hands, some hit hard, some are flat footed, some dance.
Football is the easiest. No matter the athleticism, body type or skill, there's a position for you. That's why it's the most universally played.