Darwin said his theory only works as long as every part of every complex biological system could be broken into small parts that could have each evolved over time. A system that could not be divided without losing its benefits was called Irreducibly Complex. Such a system invalidated Evolutionary theory.
DNA is Irreducibly Complex. It invalidates evolutionary theory. Evolutionary biologists don’t even have any legitimate suggestions on how it could have evolved.
That nobody can say exactly how DNA developed doesn’t invalidate the theory of evolution. Science still has its mysteries.