Astolfo said:
Spoilers aren't just about plot twists. Character deaths, story developments and so on, there are plenty of contexts in fiction where foreknowledge completely lessens or outright flattens the impact of an event/ending/etc, and that's not at all indicative of bad writing. Same thing for plot twists, if it is a central point of the plot then it's certainly not a sign of bad writing if prior knowledge of what the twist is ruins the impact of the reveal. The Prestige, The Sixth Sense, Arrival, Fight Club...
It's neat if it doesn't affect you, but spoilers wouldn't be seen as such a big deal if it didn't affect so many people's experiences.
The journey is more important than the destination, if a plot can't be enjoyed if you already know a particular plot element this mean that it was badly written.
Multiple studies have shown that spoilers has no significant effect on overrall enjoyment, and some studies even said that spoiler make you enjoy the plot even more because it allow you to focus on other parts of the plot (structure,storytelling,style, symbolism, characters development,etc...). For example Clannad after story (I took that example because I got "spoiled" before watching it) is not about Nagisa's death, it is about a man who goes through the 5 stages of grief and seeks to rebuild his life and move on
Also, reducing a film or an anime to it's plot and more specifically to a plot twist is denigrating for the cinema/animation as an medium because it's just a fraction of what's possible in cinema compared to previous medium (literature,audio-drama,etc...)
Cinema/animation isn't a plot delivery service but more a audio-visual experience.
The final twist in the films you mentioned are meaningless (especially Fight Club). What makes Fight Club great is it storytelling, compositions,filmmaking,editing, and everything that lead to that twist, not it plot "twist"...and the only way to actually spoil that movie...is to actually watch it.
Same thing for "character death", if that scene is supposed to be a sad one and is wasted by a spoiler this mean that this was badly directed in the first place because the film's director was unable to deliver an emotion through this scene.
I digress ... and this is not the place to discuss this subject.