But statements about God in the masculine don’t say anything substantive about the human masculine or the human feminine.
The only reason we can use creaturely language about God is because of the analogy of being, the participation of created essences in God’s act of existence. But because of God’s infinity, as Lateran IV observes, “between Creator and creature no similitude can be expressed without implying a greater dissimilitude.” (Denzinger-Hünermann 806) To say God is a Father or to refer to him in the masculine communicates something meaningful about God by analogy with human fatherhood, but it cannot say God is a human father, since he is the supreme spirit. And it does not say anything meaningful about human fatherhood or masculinity, since the analogy of being is effectively unidirectional: we have no vision of the Creator’s essence, so we can’t reason from the Creator to the creature.
Masculine language about God has a certain privilege because it is the language used in much of the Bible, including in the prayer Our Lord himself instructed us to use when addressing the Father (Mt. 6:9-13). Since Christians believe the Bible is divinely inspired, God obviously means to communicate something about himself when the Bible refers to him in the masculine. But the Bible also uses feminine language to speak of God: Valteryl has pointed out one reading of Matthew 23, but the Wisdom literature also directly refers to God’s Holy Wisdom, chiefly read as referring to the Second Person of the Trinity, in the feminine. And the traditions of the Church also refer to God using feminine images: for example, the image of the mother pelican for Christ, or patristic readings of God as mother (eg. Clement of Alexandria, Paedagogus, 1.6). In other words, although God has primarily communicated himself to us in masculine language, and that’s why Christians usually refer to him as a ‘he’, there is also an important analogy with the human feminine.
All in all, human masculinity and femininity are rooted in the body. God “made [us] male and female” (Gen. 1:27), complementary to one another, and the greatest of all of his creations is a woman. There’s nothing in masculinity itself, or in its analogy with the divine attributes, to suggest its superiority to femininity.
I prescind of course from the fact that the Second Person of the Trinity became incarnate as a man. Regardless of that, and the analogy between human fatherhood (and motherhood) and the divine attributes, the divine nature is genderless, since God is a spirit.
