First, Redux has been around since 2015 (and won the "Flux Wars" that had been going on for a year before that), whereas the new `createContext` API only came out a few months ago.
Second, Redux provides a lot more guidance around how you're supposed to structure your application. Context only provides a method for making values available to deeply nested components in the tree.
Third, the Redux ecosystem is huge, with addons available for effectively any use case you can think of. [0]
Please see my post "Redux - Not Dead Yet!" [1] and Dave Ceddia's post "Redux vs the React Context API" [2] for more details on how they relate.