You can find quotes [which suggest] that Anno was hoping for the audience to find meaning for themselves rather than seeking it from him.
Time and again, Anno says, not only of Eva, but of art in general, that its purpose is to communicate. And that he wishes for people to be able to gain an understanding of him through his art. For someone who doesn’t really know how to communicate with people directly, he tries to speak through visual medium. He deems his success to be in how well his viewers understand him.
In a sense, I wonder if it would even be depressing for someone to ask him what he means by something, when his entire hope is that he has communicated his meaning through his work.