In football, any code of football, I would say skill entails doing something with the ball. I believe kicking a field goal takes greater skill than blocking, though that's totally subjective and we're getting into semantics. But as you said, there are "skill positions" in gridiron football which are not the lineman.
Agree to be honest that NFL kicking isn't that hard either considering it's always from the same place and usually not that far out.