Nobody is saying it is the man's fault, or it is something you have done wrong. Heck, maybe it is mostly "her fault", who really knows except you and her?
The thing about this site is, from my observation, people here are less concerned with who is at fault, and more concerned with what the person who is willing to work on the R is willing and is able to achieve. One of the underlying principles that people are trying to get across is that the only person you can really change is you.
Doesn't make sense right? She is to blame and the advice you are given is to work and focus on you...
It is more powerful than it appears on the surface. By deciding to make changes in yourself, you are not taking the blame for where the R is at, you are choosing to take the high road, sacrificing being "right" in order to break old patterns, and strengthening yourself so that no matter what happens, you can act less emotionally and with more dignity.
The best and most succinct way I've seen this stated here is that "You're BOTH responsible for your marriage getting to this point. But since you're the one here, you get to go first."