There are TONS of single people who could tell you that finding ANY compatible person is difficult. Many of my single friends are currently in their 30's and recount horror stories of people who are either (mono and) already taken, or still single for a REASON! And they aren't even looking for a relationship structure outside of the mainstream.
Add in being open to poly, multiply by the number of people you want in your poly family (squared!) and it's absolutely going to be difficult. But anything worth having is worth being patient and working hard for, right?
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack