so you want to say, if a game needs a specific answer to a specific question given to a specified character...
.. and this all has to be at a certain time of the right day and the right place.....
.. in short you have to hit a 1 in 1000 possible combo to trigger the quest to continue, you don't blame the game design?
Dude, whenever you need a walkthrough to continue, or you have to search for hours, repeating the same stuff over and over again until you get the trigger, it's 100% to blame the dev and his game.
You are right, that difficulty IS a part of the game, but if difficulty is set too high, it's a mistake nonetheless.
EACH WAY:
Let's not getting off-topic over here