... A basic opening repertoire ... teaches [the beginner] to rely on predetermined moves instead on his thinking. ...
Most of the time, one faces a position with no knowledge of a specific move indicated in a book.
... It's not a matter of what kind of positions one will play. ...
If it is a position where the player has no knowledge of a book move, might not the player become acquainted with the problem of trying to rely on predetermined moves?
...The beginners that learn to rely on openings feel helpless even when their opponent does stupid things.
I saw a beginner praising the value of opening study and recently made a post asking advice about Scandinavian. After more than 1 year studying openings he is still unable to play 10 common sense moves!
Perhaps GM John Nunn was thinking, in part, about that sort of thing when he wrote (in 2006): "... I feel that the main reasons to buy an opening book are to give a good overview of the opening, and to explain general plans and ideas. ..."
One has to think of opening knowledge as a sometimes helpful aid.