Op, I've been in a similar position to yourself and had similar advice given.
I took the easiest (laziest) route first and stopped chasing sex, hoping that would make a difference.
it didn't, we just went from having little sex to no sex.
This was because I didn't address my approach to the entire partnership, nor grasp or empathise with my wife's perspective.
As men, we can often fall into the trap of assuming women have a similar approach to sex and a linear libido, where no matter how tired or stressed we are, we can still use sex as a kind of therapy, a release, a medicine to our woes etc.
I've learned that most (not all to be fair, but most) women do not operate that way and their libidos are very much dependant on the emotional and spiritual environment and landscape.
I eventually came to understand this and to see things from my wife's perspective. Once I understood that when tired, unsupported and unappreciated, there is no growing sexual frustration, no itch to scratch, no build up of desire just because it has been a few days/weeks, it all began to fall into place for me. The penny dropped.
Once I grasped this and tried to ease the burden where I could, show some empathy and understanding and do as much as I could to make her life easier, she began to show far more interest in sex.
I actually felt like I was being a better husband too, which improved our sense of partnership no end.
The secret is teamwork.
If you can reach that stage and there is still a miss match in libidos, then that's a different discussion, however I sense you are far from being able to assess that in your current status.