Bright, however, as is the manifestation which God gives both of himself and his immortal kingdom in the mirror of his works, so great is our stupidity, so dull are we in regard to these bright manifestations, that we derive no benefit from them. For in regard to the fabric and admirable arrangement of the universe, how few of us are there who, in lifting our eyes to the heavens, or looking abroad on the various regions of the earth, ever think of the Creator? Do we not rather overlook Him, and sluggishly content ourselves with a view of his works? (1.5.11)
Creation does shine forth God's glory. But that was, ultimately, of no value to us. Knowledge of God's existence is also a knowledge of our separation from him, perhaps even a knowledge of our shared enmity towards each other. With Him being all-powerful and holy, we find ourselves in a difficult spot.
But, we have a Saviour who is enough. A Redeemer whose life, death, and resurrection is 'profitable' to us. He takes us beyond the knowledge of God's existence to a place of being loved by God, and thereby being able to love Him back.