Human beings do not exist as men and women by accident. God created us this way for a purpose. John Piper explains:
God’s ultimate purpose for the universe and for all of history and for your life is to display the glory of Christ in its highest expression, namely, in his dying to make a rebellious people his everlasting and supremely happy bride. To say it another way, God’s ultimate purpose in creating the world and choosing to let it become the sin-wracked world that it is, is so that the greatness of the glory of Christ could be put on display at Calvary where he bought his rebellious bride at the cost of his life....
From the very beginning, God’s design in creating the universe and governing it the way he does has been to put the glory of his grace on display in the death of his Son for the sake of his bride. “Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her....that he might present the church to himself in splendor, without spot or wrinkle or any such thing, that she might be holy and without blemish” (Ephesians 5:25–27). The ultimate purpose of creation and redemption is to put the glory of Christ on display in purchasing and purifying his bride, the church....
[This] leads to the mind-boggling truth that womanhood and manhood—masculinity and femininity—belong at the center of God’s ultimate purpose. Womanhood and manhood were not an afterthought or a peripheral thought in God’s plan. God designed them precisely so that they would serve to display the glory of his Son dying to have his happy, admiring bride....
[Womanhood] is a distinctive calling of God to display the glory of his Son in ways that would not be displayed if there were no womanhood. If there were only generic persons and not male and female, the glory of Christ would be diminished in the world. When God described the glorious work of his Son as the sacrifice of a husband for his bride, he was telling us why he made us male and female. He made us this way so that our maleness and femaleness would display more fully the glory of his Son in relation to his blood-bought bride.
Read the rest here to fill in more details. The two sexes of the human race are not interchangeable or expendable. They are glorious illustrations of God’s grace towards His church, and they are beautiful.