Many reasons for the First Article of Faith
There are many reasons to hold firm to the fundamental, first doctrine of the Christian faith, expressed in the Apostles' Creed like so: "I believe in God the Father Almighty, creator of heaven and earth.." One is this: the Scriptures continually refer to God as Creator and hence to deny this role for God is to disbelieve Scripture's witness. Other reasons include the dependent nature of all reality: only God is self-existent, "the fount of his own existence."
The connection between Creation and Judgement:
Creation as witness to God
But a Gospel reason to hold firm to God as Creator is found in Romans 1, where Paul says that on the day of judgement, creation will be called upon as witness to his existence to those who say "there is no God." Here is the text:
"Since the creation of the world God's invisible qualities - his eternal power and divine nature - have been clearly seen, being understood from what has been made, so that men are without excuse." (1:20)
In other words God has wired us like this: as the human mind (any human mind) looks out at the beauty and design of the universe repeated at every level of existence from small to large, from living to inanimate, it is wired with a processing system which says "this is the work of Someone, this reveals the handiwork of Someone with greater power than a human and with a different nature than a human, Someone truly, truly great."
It is actually the same reasoning process that works in every area of life: we infer the presence of intelligent beings from design or purpose, whether in archaeology, crime or the search for extraterrestrial intelligence (SETI). This natural process will be called upon on the last day as witness to God's existence: "You knew I existed because you saw design that could not be attributed to natural forces." Creation + mind wired for inference from complex to God = basis of Judgement on the last day.
The Theological and Gospel Peril of theistic-evolution
Those then who promote theistic evolution (TE), and mean by it that beauty, planets, galaxies and all life arose naturally and spontaneously without the help of a Creator (who was only in the background, capital B), strike at the very heart of God's witness in the world, and undermine the force of God's powerful witness to himself. Where God says "look at this intricacy, it points to me, and one day if you reject me, you'll stand guilty", TE says "look at this intricacy, it all came about by itself, no God anywhere." OK, they may add that a clever God wired the constants of the universe so that it self-evolved, but by then they have undermined the power of God's universal witness to his being and character.
We tamper with the first article of faith at our peril, and perhaps worse, we tamper with it at the peril of the lost.