Yet, that approach means that G-d could have left Mary as a “single mom”, with no need for Joseph at all, and raised the baby Yeshua herself.
But, G-d understands “human nature” (having made us) better than humans understand them selves. The man-woman unity with child rearing enters our religions because it reflects the natural state created within human nature.
Often when religion is telling us that G-d wants us to do something, it is not out of some arbitrary whim of a vengeful G-d demanding we do G-d’s will just ‘cause G-d wants us to do so. It comes from the creator knowing our nature better than we do, and only seeking what G-d knows is for our own good.