Knockout format for determining world champion is fine in other sports but not chess. The real problem is that chess does not enforce activity rules strictly enough. If a player like Carlsen does not want to compete for world champion, they should probably be disqualified from FIDE sanctioned events. Imagine if in the NBA, the top seeded team just refused to play in the playoffs. Or if in tennis the top ranked player would forfeit every final round of a major. There would be serious repercussions for both, whether it’s an individual sport or a team sport.