When I first started taking the steps to regain some of my lost sanity, boundaries and detachment were kind of a combined lesson for me. The stronger my boundaries got the easier it was to detach from his chaos. The more I was free from his ridiculousness the more of that calmness I sought. It just kind of snowballed for me until I knew living with active addiction in my life wasn't something I was going to do for another 40 or 50 years.
My first real boundary with my AXH was, " I will not engage with him when he has been drinking"... that alone right there WAS detachment... and boy oh boy did it make my life less stressful. It did NOT fix our marital issues but it sure unburdened me. What a relief it was not to have to argue, cry, bargain, play nice, fake it, pretend etc anymore. The calmness that boundary brought into the $hitstorm that my life and marriage had become was like a little mini miracle.
I wasn't able to make detachment work for me as a full time solution. For me it was more like a bandaid used to hold things together while I gained the strength I needed to make wiser choices for myself. Some people are able to adjust their lives through detachment and stay married, but for me personally, that wasn't the type of marriage I wanted to have.
Interesting topic, I look forward to hearing what others have to say.