This is a question that could be answered in many different ways. If I were arguing this, my thesis would be that blurred sex roles have made families more stable and have given children a better environment in which to grow up.
When traditional sex roles were adhered to more rigidly, there was arguably less happiness and a poorer home environment for children (at least in the post-war years as many women began to want more life opportunities for themselves). Women who felt constricted by their sex roles and men who did not participate in the raising of their children in significant ways made for less happy and less loving homes. A frustrated mother and an absent father are not a good basis for a stable and happy home.
Today, with blurred sex roles, children get more of their parents and get happier parents. Their fathers play with them, help them with their homework and are seen helping with the housework. Their mothers can seem like more of positive role models as they work and as they have more power in their relations with their husbands. Relations between spouses are much more equal.
In these ways, blurred sex roles make for better families than existed when things were more traditional.