Can I say Sankhya as the oldest hindu philosophy has influenced all the other darshanas like Vedanta? That implies all astika darshanas are derivative from Sankhya, not necessarily conflicting or contradictory.
Let's get the example Advaita Vedanta vs Samkhya:
Sankhya says there is phenomenical world and the observer of phenomenical world. Advaita says there is phenomenical world and the observer of phenomenical world, but the observer is the unmanifest and the phenomenical world the manifest of the same principle - Brahman.
So, for me Advaita Vedanta looks like a panentheistic adaptation of Sankhya saying the duality is illusion because both comes from Brahman and only Brahman is real per se.
Seems like Sankhya defines the obvious relationship of human and nature and Vedanta (any school) adds the mystical view on human, nature and Brahman.
Yes, I know sankhya and yoga have close relationship, so I don't want to discuss yoga here.