Modern opening theory helps the weak, strange as it may seem. One can learn and even understand a variation without having a high chess qualification, but true strength manifests itself in positions which have been studied little or not at all. In playing [his previous move], White, in contrast to the positions in fashionable variations, quickly moves away from the well-trodden paths. As early as the next few moves, he is forced to think for himself, and this, as is well known, is the most difficult.
I've noted in the past that one of the arguments against chess960 is that, by obliterating opening theory, it somehow helps the weaker player against the stronger player; see, for example, More Arguments Against Chess960, although I could have used other sources. This seems contradictory. If opening theory helps the weaker player, how can the absence of it also help the weaker player? Who's right, Korchnoi or the chess960 critics?