The Candidates tournament has some seemingly arbitrary qualifications that players must meet, and you could argue that the format doesn't necessarily produce the strongest player to challenge the world champion.

The World Championship match itself is problematic because it gives the defending champion a fairly huge advantage, in that they retain the title if they can draw out the match, although more recently it goes to rapid chess tie breaker rounds. So in practice the Championship is decided by these tie breaker rounds, which doesn't really seem appropriate.

Given the prep time players have and the engines available, players go into these matches extremely well prepared and draws over the board are quite a typical outcome unless someone makes a mistake.

I believe Magnus wants the Championship to become a knockout tournament to reduce the advantage that so much prep time can give. There is a big difference between prepping for a field of 12 players versus prepping for a single opponent.