Some deviations are bad and criticized, others are praised.
Fischer and Capablanca didn't warn about computers
Capablanca was worried about draws back in the day when anything that wasn't the QGD practically got a ? annotation.
Fischer faced the dilemma that chess was his life, but he couldn't keep the title forever. So either his life had to end, or chess had to end. In his cognitive dissonance, he predictably protected his life, and made chess the bad guy.
For years after both Capablanca and Fischer, chess has grown. It's grown in popularity, theory (not just opening theory), and given us great fighting games.
I don't like how much opening prep dominates the very top either, but that level of play is farther away from us than most people realize I think. Anything is still possible for guys like you and me. So if anything, the bane of modern chess fans.
When I see two top GM's playing today, it feels like watching two computers. The opening lines can go on for 20 moves and more. Who wins or loses seems to be based more on who has the better home preparation and memory then who is the better player.
Capablanca, Fischer and many others have warned about this problem. It seems to me that the top players today are young and play very antiseptic chess. Technically proficient no doubt, but hardly appealing. Those that try and deviate and play more creatively ie; Morozevich, Shirov etc, don't stay among the the top for very long.
I was reminded by this when playing over the recent Nakamura - Eljanov game where the former deviated from theory and was roundly criticized and went on to lose the game. His opponent joined in on the critcism in a later interview. I guess Nakamura should have stuck with theory to God knows what move, before the two finally got around to actually making moves on their own. That or sprung some novelty prepared by a computer.
I had really hoped that Chess960 would have replaced the old game by now. Kill the opening, and we would truly see who is the most talented player around. It may very well be Nakamura. To his credit, he does go against convention. Very few top GM's these days even try. This means however, that he may never be World Champion. This style doesn't lend itself so well for match play. He might have to temper his play, and play the more dry, technical, colorless chess that most of his top competitors play.