If you're someone coming from other first-person shooters (FPS), or you're just super used to hitscan weapons in Overwatch, Hanzo might be a little tough to learn due to his lack of a hitscan weapon. The arced travel of his arrows is unique in Overwatch in its style, but once you get the hang of how said arced travel works (the arced travel is different depending on how long you charge the shot up for), you're good to go. At the end of the day, it just takes practice and determination, and the learning curve will vary depending on how much experience you have with hitscan weapons and/or weapons with an arced travel in FPSs.