If "academics have begun writing about cultural evolution" then it seems the notion is a recent one.
That rules out 'archaic' and 'outdated'.
IF 'the notion' referred to Darwin's ideas, then perhaps you could say they were being abused or misused: but it doesn't. The notion is: cultures evolve in Darwin fashion.
That leaves divisive and derivative.
The notion is that 'cultures evolve in Darwin fashion'. Therefore to say it is derivative is tautologous. Of course it is derivative: it derives from Darwin.
That leaves divisive.
BUT the rest of the sentence tells us only that "few [academics] treat the underlying Darwinian logic with the care it deserves." It doesn't tell us they are particularly divided.
Not treating something with the care it deserves might be described as misuse or abuse.
So I think the question is badly constructed. For it to work it has to be rephrased so that the inserted adjective will describe Darwin's ideas. Perhaps like this:
Few ideas are more _____ than those of Darwin in the notion that cultures evolve in Darwinian fashion. Many academics have begun writing about cultural evolution but few of them treat the underlying Darwinian logic with the care it deserves.
I would go for 'abused' and keep my fingers crossed.