Spirited, all I can say is that is not my experience in the past, I have never had trouble locating partners for poly, did it work in all cases, no it did not. That is not to say I will not have trouble now, I haven't looked for 10 years, there is a difference between then and now, I am 10 years older. But I have had a quad that worked just fine for a long time. Eventually it became obvious to me that the quad wasn't working as well as it should and I ended up having to get the one girl who just wasn't getting it and having issues with the other girls out of the relationship. We found someone and got her married and she has been so for several years now. My triad stabilized and we were extremely happy for the next several years.
I understand that you had a bad experience with poly, but a lot of people have had trouble with standard relationships too, does that mean all of them are bad. While I understand most women are not going to stand up and say "I want poly as a first choice" I think that there are more out there who would risk it if the chemistry is right than you think.
I will say this for sure, term unicorn means so rare it doesn't exist and if that is the case how do you explain the fact that while we are a minority, there are a significant number of poly families out there. Do you think the Dominants go out and kidnap them and hold them in prisoner. Women join a couple to form a triad because the couple can bring something to her life she cannot find anywhere else. That something else is a real family who will love her and help her to be the best she can be.
I have been in the life for a long time, while if you just look at the numbers on websites like this, it makes it look like there are a lot of dominants and only a few submissives, nothing is farther from the truth, there are a lot of submissives both male and female. There are a lot of tops who call themselves dominant and or master, but they are tops and they are primarily interested in straight bdsm play. Lifestyle dominants, the kind that form families are much rarer on the ground, the only thing rarer is fem doms and neither of them are rare enough to be called unicorns. For me success in this lifestyle, couple, triad or more, is does it stand the test of time. Relationships that last the years are the solid ones, not the ones that flash and burn, it simply doesn't matter what the relationship, just is it good and does it last.