When I was fighting addiction and my own mussar was not working for me, I had no choice; there was no Shlomo Hamelech to go to. So I went to the practical experience of millions of addicts.
Their experience is that the basic prescription of AA co-founder, Dr. Bob (see a copy of his prescription here) to:
(1) Trust in G-d
(2) Clean House
(3) Help Others
is just what the addict needs.
And their experience is, that these three precepts are most easily achieved through the 12 Steps.
And their experience is that the best way to get the 12 Steps, is by working one-on-one with someone who has experience of the same addiction, and who experienced overcoming that very addiction by using the Steps.
This is how it is summarized in the AA Big Book:
"One alcoholic could affect another as no non-alcoholic could... Strenuous work, one alcoholic with another, was vital to permanent recovery." (p xvi-xvii)
Does this mean that we need to get defensive about the supremacy of Torah? Absolutely not. Mussar, as R' Yisroel said long before the AA Big Book was ever written, depends on experience. And fortunately, our Rabbeim have no experience in addiction.