As important as attachment seems, I think that other factors might be more influential on human development. I see the argument of nature vs. nurture being very applicable here because to me the things that we grow up learning and the feelings and attitudes we naturally develop can really affect the outcome of our lives.
I agree, the attachment argument centers around the idea of naturally associating with a parent, however it is also possible that outside influences have a strong effect on the outcome of a person's life.