Joseph Smith talks about the authority of the priesthood being unable to help those who have the spirit of the devil and are willing to keep it. What does this mean? While I think his meaning is fuller, I think it has relevance to a common situation today.
It means, in part, that the ability of the priesthood to "cure" pornography addiction is pretty darn limited. And that is because invoking the word "addiction" fails to capture the reality that each time one indulges in pornography is a conscious choice. You may as well give someone a blessing to stop them from sleeping around.
Specifically, the issue of being "willing to keep it" means that when push comes to shove, they aren't really willing to simply stop doing it. And indeed, until they are, what can God do for them? There is no divine way to revoke agency.