TLDR: Real life and real people are ambiguous. If you want your writing to be realistic, be strategic about how you employ ambiguity.
We want to breathe life onto the page, make the unreal seem real. In an effort to do so, we often rely on explicit descriptions, leaving no detail to be confused and the reader’s mind with all the tools to imagine.
This is particularly true for fantasy writers. A dragon is a thing with an exact form and attitude. Dragons are scaly, big, fire-breathing, often greedy (in the west anyway). Dragons, in fairy tales, epics, and modern fantasy, are often easy to comprehend and understand, as opposed to real humans, who are self-contradictory, complex, and ambiguous.
A good contrast is H.P. Lovecraft. His creations are beyond the complexity and mental faculties of humanity, so much that they drive characters to madness. Lovecraft’s perpetuation of the irrational and ambiguous make his work endearing and enduring.
“The most merciful thing in the world… is the inability of the human mind to correlate all its contents.” -Lovecraft
John Crowley, author of Little, Big and the recently published Ka, has this to say on the matter:
“I wanted to write novels with the breadth and depth of the greatest realistic fiction — my models were Dickens and Flaubert and Nabokov — yet with an element of the non-mimetic, or irreal, or preternatural, whatever the best word might be. And that meant not just positing such things but giving them the ambiguous and never-fully-plumbable depth that things have in realistic novels.”
So be ambiguous because life is ambiguous.