Is there any symbolic meaning to the images of the windmills as in referencing economic and social issues that would give light on what Cervantes is attacking?
This is an interesting notion, but the text does not encourage this interpretation. The essence of the novel is that Quixote, in his deluded state brought on by reading too much Romance literature, sees everything in the real world as some element in the Romantic world. The large size of the windmills, together with their moving "arms," give Quixote the delusion that they are giant foes to be defeated. While the novel does parody Cervantes' real world, his complaints are not economic or even social, so much as moral and ethical. Windmills were ubiquitous in Cervantes' time, and there is no evidence that he had any specific complaint against the granaries that used them. The literary device here is personification, giving human form to inanimate objects. Quixote also mistakes a prostitute for a high-born lady, but Cervantes is not criticizing the profession; at most he is lamenting the descent of womanhood from its pedestal in earlier times. (Having said this, however, let me encourage you to continue making these speculative leaps as you read; they can be fruitful.)