Chovos Halvavos challenges the idea of “emunah peshutah” for someone capable of deeper understanding. Relying on the emunah we inherited may be sufficient when a person lacks the ability to investigate further — but someone blessed with a capable mind is expected to use it in the service of Hashem.
Rabbeinu Bachya illustrates this with the fascinating parable of the king’s two tax collectors. Hashem doesn’t expect the same thing from everyone; He expects us to use the particular abilities He gave us. And for someone blessed with intelligence, intellectual laziness in matters of emunah is itself a failure to serve Him fully.