The traditional family is in many ways compatible with our biology. The only way in which it is not compatible with our biology is that it encourages fidelity for life. But that flaw is exactly what makes it allow for the high levels of productivity that it allows for. There is a price to be paid for everything and in the traditional model the price we pay is denying ourselves the joy of sleeping around. In return though we get a system which is compatible with our biology in almost every other way and so we are almost guaranteed happiness.
We get a system which encourages the natural bonding between children and their mothers which many scientist and the attachment theory speculates to be a major contributing fact to the confidence and overall happiness level of the children as they grow into adults. A system which ensures that toddlers have lower levels of the cortisol stress hormone which does affect their behavior. A system which allows mothers to breastfeed for as long as they wish to and feel free to become pregnant without interrupting their careers. This has health benefits for both mothers and children.
A system which allows mothers to bond with their children. A system which allows fathers to play an crucial and indispensable role in family life, ensuring their presence as role models. We get a system which respects the primitive desires of men and women. It respects the desires of women to mate with a man that can support her and her offspring, and the desire of men to mate with women who will not mate with other males, ensuring that they do have offspring. We get a biologically compatible system which has the power to make individuals extremely happy.
In short the traditional model is bliss sprinkled with fidelity!