Not just a blunder, but a blunder made too quickly when he had plenty of time. If Nepo won a third straight candidates (he's automatically qualified) that would be an extremely impressive achievement that would be a first in world history I believe.
Chess has moved on significantly since Magnus first became champion (partly due to the man himself).
If Fide is struggling to move with it, there will be a limit to what it can ask of its dominant figure in the context of an event that requires huge investment in time, money and energy for participants.
Currently the World Chess Championship is just a collection of very talented chess players spending months having supercomputers evaluate positions looking for the slightest imaginable edge.