Yuri Dokhoian said it...

      I came across this in My Great Predecessors, Volume 2, where Kasparov wrote, “As my second, Yuri Dokhoian wittily expressed it, with the years each world champion begins to ‘calcify’ – in other words, to become inflexible and be transformed into a living monument. That is, he gradually ceases to add something new to chess and to grasp at the dominating tendency of its development. And sooner or later the inevitable retribution sets in since the young challenger, on the contrary, usually makes a step forward.
      Reminds me of Shirov’s comment about his meeting with Botvinnik where they discussed the Botvinnik Variation and how it was of no interest; according to Shirov, the old man was stuck on insisting a particular line was the best even though Shirov knew it had been considered inferior for years.