What kind of story world is presented in "The Ones Who Walk Away From Omelas" by Le Guin?

At the beginning of the story, the world presented seems like some idealistic utopia. It seems like a paradise. The world is full of joy and this is exemplified by the upcoming Summer Festival. The people are happy but still as complex as we are. The notion that happiness must correlate with simplicity or even ignorance ("ignorance is bliss") does not apply to Omelas. In other words, these people did not have to sacrifice knowledge,...

At the beginning of the story, the world presented seems like some idealistic utopia. It seems like a paradise. The world is full of joy and this is exemplified by the upcoming Summer Festival. The people are happy but still as complex as we are. The notion that happiness must correlate with simplicity or even ignorance ("ignorance is bliss") does not apply to Omelas. In other words, these people did not have to sacrifice knowledge, complexity, and even some luxury in order to obtain this kind of joy. They are not "noble savages" living in simple purity. They are complex, we might even say Modern in some ways, but with the same notions of joy and happiness. It is, in a sense, too good to be true. But this is false. The narrator reveals that Omelas is not perfect. Therefore, it is not too good to be true. In fact, it is actually more realistic than at first described. 

The happiness of Omelas depends upon the suffering of one solitary child. There is no explanation of why this agreement has been made or with whom. The bottom line is that the majority of Omelas live in joy and peace as long as one child suffers terribly. So, it is not the perfect utopia it seemed to be in the initial descriptions. In fact, it bears striking resemblance, literally or at least allegorically, to cities and towns in actual existence. Aren't there cities, towns, and nations where a large portion of the population is relatively happy but a majority of that same population suffers? And although some people protest the suffering of others, doesn't it seem that most people simply accept the fact that while they are happy, others will suffer? These are some questions that the story suggests. So, the world of the story initially seems idealistic, but in the end, it seems all to realistic.