Former world champion JR Capablanca was not a particularly good opening player. Yet he was the "champ" because once he survived the opening, he played better middle and endgames than others. And this occurred because he was able to play a handful of openings time and time again.
Late in his career, he had particular difficulties against Russian masters. Not only the stars like Alekhine, Botvinnik, and Keres, but even second-rank Russian players. A major reason was that they played varied and complicated openings, and got the "jump" on Capablanca in this part of the game.
Why didn't non-Russian players do more to take Capablanca out of his familiar opening lines?