It's perhaps akin to how when a person goes into therapy, the first step, if practical, is to deal with any substance dependency issues. At least where I live, it's a prerequisite for further therapy (barring acute needs, perhaps).

I wouldn't be surprised if this is Peterson's thinking too, although I also wouldn't be surprised if Peterson doesn't know what the 'next step' might be (or is hesitant to recommend it).

At least based on my experience, both a good thing and a failing about modern therapy (and if I understand correctly Peterson is primarily a psychologist/therapist) is that it explicitly does not get too much into the stuff beyond a 'direct', pragmatic kind of mental health. For the rest you're encouraged to look elsewhere or cobble something together yourself.

(this in contrast to, say, priests/pastors/etc.)

The fact that you are looking for it means something.