In my opinion, up to a very, very high level, the importance of opening knowledge is vastly overrated.

The two highest rated players in the world (Carlsen and Aronian, neither of them participating in this world championship match) frequently just aim to get a playable position out of the opening and still succeed in outplaying very strong opposition in the late middlegame/endgame. This despite the fact that it would difficult to find two better examples of "human chess databases".