Even though it does not contain doctrine of the atonement?
A creed is NOT Scripture. It is not a complete statement of everything that we believe is Christians. Frankly, it doesn't need to be because we HAVE Scripture. So, even though the creed doesn't have a statement on the atonement, it matters not because I do not take the creed as authoritative. Rather, it is a statement of faith. Incomplete, but valuable for a general understanding.