In "Knives Out", a mystery, it's asserted: "The complexity and the grey lie not in the truth, but what you do with the truth once you have it." What does it even mean?

I haven’t figured it out yet what it means. And yet, it’s simple, plain, old, English. I mean, what am I missing? It could be the greatest discovery in the world of the complex mind games of mysteries, or the greatest misleading incomprehensible loads of R-U-B-B-I-S-H I’ve ever had the pleasure to take an interest on, your call.