I quite agree any notions of God we conceive in our minds are puerile attempts at fitting of God into our imaginations.
In so far as Christianity is concerned, however, it is God who has chosen to reveal Himself over the course of about 6,000 years.
Whether we believe in that revelation or not, normatively we can have accurate conceptions of God in contexts within which it is God who reveals Himself to us.
Consistent with difficulty of fitting of revelations of God into our minds, outside of revelations of His character, God remains much of a mystery in Christian Scriptures, the Bible.
Perhaps then, a non-mysterious concept of God is evidence of an imagined as opposed to a revealed God.