Earlier quoted context omitted.
Darwin's theory of evolution is descent with modification. It requires a method of inheritance, a method of random variation, and the observation that a variation which results in more descendants will grow exponentially relative to the rest of the population, until it dominates. Examples of specific theories include the Modern Synthesis and Punctuated Equilibrium. But there are more specific theories as well. For ex…
The problem of dark matter is, "why does lambda-cdm fail in all these ways that makes it look as if there is a bunch of non-interacting stuff in the universe?" There are specific theories that address the problem, but none is the theory of dark matter. Likewise, Darwin started off with the problem, "what is the origin of species?" answered by natural selection, and its progeny as you mentioned. Again, I'm being nitpi…
Dark matter is no more or less a theory than Darwin's Descent with Modification.
Darwin's theory needed to be modified extensively to deal with genetics. And modified again to deal with paleontological evidence on how speciation works. And modified again for jumping genes. And modified again to cover things like having a virus create a new clade of Mammalia by hybridizing mammals and a parasite. And yet we still talk about Darwin's theory of Evolution.