Nietzsche is systematic

He is in fact a systematic philosopher..

His system is to collapse every possible dualism or dichotomy or pair of opposites he can find.

Truth vs Error (truth is just errors) Morality vs Immorality (morality stems from immortality) The Philosophy vs The Philosopher (Beyond Good and Evil §6, you cannot separate the philosophy from the philosopher) Pain vs Pleasure (more pain, more pleasure, not opposites but reinforce each other) Action vs Personality (you cannot separate the action from the personality, for example you cannot separate the birds of prey from the predatory behavior, this claim is that there is no free will essentially). Good vs Evil (the good for the masters is evil for the slaves). Rationality vs Irrationality (Our a priori forms of cognition are the most irrational beliefs we can’t refute). True Self vs Apparent Self (there is no “true authentic self” behind the masks we wear and our drives). Mind vs Body (mind and body are the same, there is no free will, no soul, no ego that governs the body freely and rationally). Drive vs Action (again, no free will, you cannot separate the drive from the action itself, the drive IS the action). Appearance vs Reality (appearance IS reality) Cruelty / Schadenfreude vs Mercy / Compassion (Nietzsche thinks mercy is cruelty, and that compassion is schadenfreude, he thinks that’s the reason we have such reverence for the symbol of the crucified is cruelty).

He does say in Beyond Good and Evil a few things about opposites:

““How could something arise out of its opposite? For example, truth out of error? Or the will to truth out of the will to deception? Or selfless action out of self-seeking? Or the pure sunny look of the wise man out of greed?”… The fundamental belief of the metaphysicians is the belief in the opposition of values . Even the most careful among them has never had the idea of raising doubts right here on the threshold, where such doubts are surely most essential, even when they promised themselves "de omnibus dubitandum " [one must doubt everything]. For we are entitled to doubt, first, whether such an opposition of values exists at all…”

Section 24: “…For if language, here as elsewhere, does not cast off its clumsiness and continues to speak about opposites, where there are only degrees and many subtleties of gradation…”

Also there is the reoccurring idea of perspectivism, about morality, truth or values.. There is the perspective of the strong, and the perspective of the weak. There is no one truth, only a multiplicity perspectives.

But he is so brilliant at hiding his systematic approach to philosophy in his aphorisms, that we come to think that he is ant-systematic. If he presented this as a system his thought would become boring..