I have the following sentence from my hero academia anime.
つくづく あの入試は 合理性に欠くよ。
The english subtitles for the show have this as the translation "That entrance exam was definitely not rational enough."
I'm confused at how に is working here. I know that に can be used for nouns that take the copula (na adjectives) to turn them into an adverb but 合理性 isn't one of these na adjectives. I would think を or は would make more sense here. Is に perhaps acting as a substitute for は here?
I've ruled out this acting as an indirect object marker and a direction marker. From there, I'm pretty clueless as to what it's exact function is here. Can anybody help me out here?