If you read the Catechism I referenced it explains the Church’s explanation for why they say what they do. The church actually will refer to God in a feminine sense sometimes.

The TL;DR of it though is that if you think of your own parents, you are made from the matter of your mother. Your father’s DNA provides the design. In Catholic theology we are not made of what god is made of, so calling god our father is simply more accurate in human terms than mother.