FY, the comments from MLCers you post are interesting. In my case, my W has said on occasion that "it is her" etc. But she'll also say how that of our 22 years together she may have loved me for 2-3 years. So it is both her but also the marriage.
I guess we are here for a few reasons. First, we don't believe that our S fell out of love with us, rather we believe that it is temporary. Second, as FY states he is a better person due to the crisis, and I feel the same way. My W's MLC and ILYBINILWY really rocked my boat and I've changed in ways that I probably would not have. I'm pretty happy with the changes. No matter what happens, there's that.
If we're wrong about the Spouse's lack of love being temporary and it turns out to be the new state of things, then all we are doing is spending a few years in transition from marriage to separate and divorce.
For me right now, I still prefer marriage, I think my W and I had a good relationship, and can have an even better one. I'm still willing to wait and see. However, I also realize that if we separate, I'll be OK too.