My ex and I did couples therapy when he was actively using. It didn't work and the therapist said there was no point in us continuing in couples therapy and we should seek individual therapy. I went in to talk about what his drug use and alcoholism was doing to us, him, and me. He was 9 years sober when he first relapsed. I had never known him not sober so it was a huge change in our relationship and I was so lost in what to do and how to help him find sobriety again. He would stop for brief periods but never embraced sobriety and so it was still just as miserable.
He went into the sessions with the attitude of I am an adult, I am choosing to use, that is what I plan to continue to do and you are the one with the problem. Which I guess was true, I had a problem with the drug use - he didn't. He also claimed that the problems in our relationship didn't go away when the drug use did. Again true, but when he would stop he was just dry - not working a program - and I didn't know I needed to work my own program. I found my way to Al-Anon a couple years later and I regret waiting so long to save myself with my own recovery.
The therapist tried to convince my ex that if he wanted to start addressing the "real issues" in the relationship the only way to do that was for him to get sober as that had to be dealt with before we could get any deeper. He was like no thanks and the therapist was like this isn't going to get anywhere so we ended the sessions.
If you did try to do couples therapy I doubt it would last long if he isn't willing to stop completely, unless you ended up with someone not familiar with addiction and that would end up a mess.