There is a potential technical route that would allow Scrivener to “defer” the complexity of dealing with citation styles by bundling a CSL engine, as suggested here:
It would still require a reference manager program to generate the bibliography database, and all Scrivener would do is find-and-replace citation keys with formatted text provided by the CSL engine at compile time.
Pandoc does allow you to generate full citations directly from a Scrivener compile however (it does have a full CSL engine), and provides a whole bunch of other benefits for academic users; see my scrivomatic workflow for reasons why.