This is a God of the Gaps Fallacy.
Let me take you to an example.
Imagine an ancient tribe who experiences droughts or dry season. Crops are withered and there's no water to drink.
Probably, this ancient tribe will think that this is a punishment from the Gods. That this drought is originated from God.
But today, due to our sophisticated knowledge in meteorology. We can understand why droughts happen, and even predict it based on our advanced equipment. We know now that droughts happen because of changing weather patterns.
Then where's the God explanation that ancient tribes use?
It is replaced by our knowledge and science.
Let me take you again to a second example.
Imagine, a thunder strikes. People may wonder where the hell it came from. But an explanation to the ancient Greek were used and believed in that time. It was Zeus the god of Thunder.
But today, due to the knowledge about meteorology, we are able to understand how a thunder is formed and thus removing Zeus the God of Thunder from the equation. It is replaced by our knowledge in Science.
Let me take you today, in the present time.
We still don't know how the universe is formed or where the heck did the DNA came from. Because we don't understand them yet like in my previous examples.
And concluding that "God did it", we will stop exploring the world and thus limiting our knowledge in Science.
We may not know things yet, and WE MIGHT NOT KNOW THE ANSWER, but we will figure it out.
Imagine a world where everyone is saying "God did it". We wouldn't be able to examine the natural world. There are no medicines, computers and even we might be stuck in caves and passages because we are not curious enough.
But, we do have other theories that explain how universe is created, we have countless theories. One is which the Big Bang Theory which is formulated by the same scientific method that is used in our medical sciences, meteorology, physics, etc.This theory may not be complete nor doesn't explain the origin of what the heck is universe like.
Also, IT IS GOOD THAT WE DON'T KNOW, rather than knowing without evidence. We still don't know yet, but we will figure it out. And if that makes you uncomfortable, you can always resort to fantasies, it's harmless unless applied in society.
And by saying that "God did it", we are limiting ourselves from discovering what wonders of the mysterious universe has to offer in our hearts.