I don't think "can be used to gain access to systems" is a good working definition of "useless".
I think you mean something like "changeable" or "able to be made secret again". If someone finds out you're bribing the police and publishes it, you obviously can't change that fact or somehow directly mitigate the damage. But some privacy issues are more like passwords, they cause damage only in the right situations, and the window can close.
So while there are differences, I don't think there are two neat categories like you suggest.