I'd say its quite the opposite,actually. Parables can be used to make something more clear, explaining it in laymans terms if you will. Anyone can read a parable and understand what is being said. Prophesy on the other hand, is done in quite the opposite way, turning something that should be simple and clear into something that is unclear and open to interpretation.
As for the natural man not being able to understand piritual thing, I don't buy that either. If that were so, no one would ever become "spiritual" due to lack of understanding. Its also a cheap cop out when someone pokes holes in an argument. You simply say that they can't understand it because they lack some sort of hidden knowledge that you posses. It allows the supposed holder of this hidden knowledge to not be required to try to explain their unsupportable position while at the same time allowing them to feel superior to the "natural man".
