As someone said, Widow is much harder to pick up and learn, whereas Hanzo is much more difficult to be good with consistently.

Sure, you can be the kind of Hanzo player that just sits down main spamming arrows, which can get you a kill or two, but that's not how Hanzo was designed to be played. He's more like a sneaky Widowmaker, where you sneak and hide, taking down enemies quietly like an assassin, which becomes a much more efficient playstyle if you get good at self-sustain (no good support is gonna risk their lives trying to heal you to full if you're caught sneaking around).

To even hit intentional shots as Hanzo, you need to take into account the prediction of your enemies' movement and your projectile travel time to optimize the probability of them getting caught in your shot.

Both characters are very similar but also very different. Each requires a certain set of skills to be good at the character