I think I've read something about a CRISPR experiment failing because cells would correct the changed sequence back to the original...I'll see if I can find it.
This is, to a degree, what happens. However, a species that ages has an advantage in that new individuals, with perhaps better characteristics in the face of new circumstances, have access to more resources.
I do wonder whether there is a point where the lost experience of other individuals weighs heavier than physically better adapted individuals. In a way, culture serves as a way to preserve information that would be lost by aging.