When I was a child, I got the idea to write a tool to generate 16x16 , 4 color sprites by randomly generating pixel heaps, reviewing and rejecting sprites manually, which did not look good. The idea is basicly a procedural content generation tool, thought doing some basic math, it was not a very promising idea.
But it is a good comparision of the situation of procedural generation. Back then I would have seen images in randomly generated pixel heaps, much like your brain is able to see figures in clouds. But today we no longer have 16x16, 4 color sprites, we have artistically crafted, huge paintings. Even realistic rendering is really stylized, utilizing many tricks to communicate some important emotions and messages in just every possible detail, and here we are at the point where procedural content breaks.
You can compare it with reading a book and watching a movie. While reading a book you use your imagination to build a living world from some fix points, whereas while watching a movie you are confronted with a given vision, not really able to bring in your own imagination.
Now think about something in between book and movie. No idea, me too, I can't see how it should really work, and I'm not seeing how real procedural content should work in a modern game without abstracting the visualisation.
I have experimented with procedural level generation for more than 3 or 4 years in my game now. The major issue was, that it feels, well generated. I think, that people who play an abstract game (rogue-like or minecraft) stepped already over the suspend-of-disbelieve threshold, therefore accepting to live in a procedural world. But removing the abstraction puts the pattern of generated content in the foreground which results in breaking the suspend-of-disbelieve for many people. Much like the uncanny valley, we have the situation that the improvement of a single aspect (visual) change the awareness of the audience, suddenly seeing flaws in details (generated vs design content) which were not previously an issue.
So, I'm the only one having this trouble ? Besides terrain generation, what game should have procedural generated content and the options and budget to archieve it ? At least diablo 3 should have and indeed they have kind of procedural content in a huge, painterly world. But taking a closer look, you will see that they are only really plugging together template created by some artists, which must not be bad, but which is not really what I would have expected, or hoped for. But I'm sure that the people over at blizzard looked for a way to maximize the content generation while keeping an artistically and lovely art style and environment.
Procedural content, much like art, must be consistent with the rest of your game to work properly and the current state of procedural content generation was not able to keep up with the pace of visual content creation making it really hard to incoperate it in a modern (non-abstract) game.
Therefore my final thought is, that you should consider to utilize the human brain to make sense behind procedural, though abstract, content, instead of making procedures which are able to simulate the human brain to create artistically content. The first worked so far, the latter not.