Yes, "depth" is used in several ways. Some little points -
- I recently read that the parables weren't supposed to be easy - "for those outside [i.e. non-disciples] everything is in parables; so that they may indeed see but not perceive, and may indeed hear but not understand" (Mark 4:11-12)
- It seems to me that many poets today are praised for work that is quite incomprehensible to the ordinary reader. Why is this? (Barbara) - because "the ordinary reader" has changed? The ordinary reader has at least a Creative Writing degree now, and has read lots of modern poetry. Perhaps there's felt to be less of a need to offer an inviting surface.
- making sure their readers understand what they're talking about is not important (Barbara) - I'd guess that nowadays "to understand" is less likely to mean "to be able to paraphrase". Perhaps the paraphrasable element was always the least important part, the easiest to talk about. It's rather harder to say why you like a melody or a Pollock, or an Ashbery