I believe everything should be put in perspective. Other than Paul Morphy, Fischer is probably the only World Champion to have learned chess on his own with no private coach to give him lessons. By the early 2000's computers were strong enough to beat the top players in the world and Carlsen along with every modern grandmaster today have benefited from that.
Fischer could have been world champion long before 1972 but was fed up with FIDE and the way the Soviet players would agree to grandmaster draws to give them strong advantages in crucial games. Fischer and Carlsen are the only players in modern history to voluntarily give up their titles and both were about the same age when they did. Did Fischer realize that he had reached his peak and that some young lion would inevitably take his title? Possibly, but maybe Carlsen was also thinking the same thing when he abandoned serious chess and decided all his attention will now be on skittles. Here is something very interesting.
“Worry about Fischer led the All-Union Scientific Research Institute of Sports, which studied the psychology of sports, to appoint a Soviet grandmaster and theoretician, Vladimir Alatortsev, to create a secret laboratory (located near the Moscow Central Chess Club). Its mission was to analyze Fischer’s games. Alatortsev and a small group of other masters and psychologists worked tirelessly for ten years attempting to “solve” the mystery of Fischer’s prowess, in addition to analyzing his personality and behavior. They rigorously studied his opening, middle game, and endings—and filtered classified analyses of their findings to the top Soviet players.” ― Frank Brady, Endgame: Bobby Fischer's Remarkable Rise and Fall - from America's Brightest Prodigy to the Edge of Madness
“Bobby announced that he’d never again participate in a Candidates tournament, because the FIDE system made it impossible for any but a Soviet player to win.”
― Frank Brady, Endgame: Bobby Fischer's Remarkable Rise and Fall - from America's Brightest Prodigy to the Edge of Madness
If anyone thinks that is far fetched, just remember that the Soviets were so surprised at how easily Fischer was defeating Spaasky that they even examined the chairs to make sure Fischer wasn't cheating somehow.
Carlson