A least some of this is the characters movements have no context. They're making gestures that might look more natural if they were talking to another character

A least some of this is the characters movements have no context. They're making gestures that might look more natural if they were talking to another character but they're standing alone on a bridge. There's also no realistic gravity between their feet/body and the ground or objects around them. They pop up and down if there's a step and appear to be floating.