Some players like Sultan Khan, a slave and the Peruvian grandmaster Julio Ernesto Granda Zuniga, a fruit grower shocked the chess-world in the past by the contradiction between their excellent tournament-results and their very limited knowledge of the openings. With a minimum knowledge of chess they managed to beat experienced masters. It seemed like they solved the code of chess.
It doesn't surprise me that some players believe there exists a key which can solve chess. Now and then I hear scornfully certain theories proposed by players barely knowing more than the basic rules of chess. Of course pure nonsense as natural talents have never discovered any specific key.
Shortcuts to become better in chess don't exist. Except a few rare talents the road to master chess is very long and full of obstacles. Building up experience is very important but it is doubtful if this is sufficient on the long term to keep making progress. Definitely once +2000 rating is achieved, study at home will become an important catalyst to improve.
At home we can work at chess in many different ways but probably the most important is still analyzing critically your own games. I always put a lot of effort in it as e.g demonstrated by my old article which games to analyze. I know some people consider my diligence exaggerated (see e.g. this reaction) but I don't think this is justified. A recent case once again proofed this. In 2010 I lost in a dramatic way my last 2 rounds of Open Leuven against strong opposition. This destroyed any good ranking see the summary table. I start with the very painful defeat against the Indian IM Satyapragyan Swayangsu.
That game was just finished or I had to play already the last round against the strong Belgian FM Hans Renette (another player whom quit chess a couple of years ago). A handful minutes of preparation wasn't enough to build an answer for his repertoire.
I learned from the 2 losses some valuable lessons and recently I was able to profit from this acquired new knowledge. I got exactly the same opening on the board in round 8 of the Belgian interclub as in my game against Satyapragyan.
It is pity that white had no time to continue playing but it is clear that blacks opening was a success. Coincidentally exactly the same happened in the round 9 of the Belgian interclub but this time with the same opening of my game against Hans.
Indeed it can take a while before we see any return from all the hard work done. I can imagine that many players don't have so much patience and prefer to quicker variate between openings instead of persist the study. Besides a good memory is vital which is not something everybody has automatically. Anyway this double victory tasted extra sweet.