The two major problems with couple's therapy are:
1. Both people have to actually be willing to change their behavior and open to listening to what they're doing wrong. Most people, especially women in my experience, lack the ability to ever truly agree they are in the wrong in their relationship and usually just want a 3rd party to tell the man "how it is" and how he needs to be better to her. In both of my experiences with a couple's therapist, my two separate LTRs both had that mindset that we were going there because I needed to be better towards them. It is basically a non-starter. The couple's therapist I went to with my first LTR actually told my LTR she needed to change her behavior. My LTR subsequently refused to go to her anymore (shocker) and the relationship was over soon after.
2. Most couple's therapists are not very good at their jobs. Take a look around and read up on these people and you can clearly see immediately they aren't people you would ever get advice from about much of anything, let alone how to run your relationships. Exceptions exist, but they are a minority. I had a particularly bad experience with the couple's counselor I went to in the second LTR I experienced it with. He was exceptionally biased towards her and everything in every session was typically about what I should be doing to make her more comfortable. I eventually refused to go on with him and I actually ended the LTR not soon after. The guy had impressive credentials, but was horrible at his job as he chose to view the relationship through a microscopic lens of hers and not listen to both sides -- at least not in any effective way.
Based on the above, couple's therapy very rarely works effectively for those reasons. It is a huge time and money sink and not worth it IMO. If you can't fix the sh1t on your own, the writing is likely on the wall.