Darkness-Induced Audience Apathy is when the audience is put off by the incredibly dark nature of a fictional work and won't care what happens next, lose interest or want all the characters to die off. For example, A Song of Ice and Fire can cause this due to its cynical tone, characters making morally questionable decisions in order to achieve their goals and many of the villains being irredeemably evil.
The reason I'm bringing this up is that my trilogy, The Ragnarǫk Cycle is pretty dark. The protagonist is incredibly self-centred, an existential nihilist and suggested to be suffering from depression. The only person serving as his moral compass is heavily implied to be insane, uses her religious faith to justify some rather... dubious actions she committed and secretly wants to die.
Said protagonist and deuteragonist are pawns of a military organization crippled by corruption and its politically correct dogma (think a more "progressive" version of Blackwatch) in conflict with parasitized humanoids, who seek to eliminate all forms of discrimination, by turning humans in genderless parasitized humanoids and "cleansing" themselves of people with disabilities and other undesirable traits. Things get even worse when later into the series, this organisation crosses swords with a cult that worships and is dedicated to unleashing a soul-devouring, omnicidal, aeons-old monstrosity responsible for the downfall of countless interstellar civilizations.
I plan on having several moments of levity strewn throughout the series (although I'll trying my best to ensure that they don't cause tonal disparity), having my leads become better people through the power of character development and the series becoming less cynical with each installment. However, I feel that readers will still think that I'm trying way too hard to be controversial and "edgy," rather than being concerned with trying to tell a good story.
So, what are ways to avoid Darkness-Induced Audience Apathy?