What message do you think Fitzgerald was trying to convey to his reader about the relationships that were affected by wealth or stature in The Great Gatsby?
Our sense of humanity can be blunted and distorted by artificial desires and misguided values. I think this is one of the messages of the novel.
Gatsby almost literarally loses himself in the pursuit of wealth. Daisy is prepared to leave her husband, in part, because Gatsby has such beautiful shirts. Love becomes just another facet of the material fixations embodied in so many of the characters.
So, to be more direct, we might say that the comment here is not that wealth destroys relationships but an exaggerated value placed on the pursuit and possession of wealth can lead to a more general distortion of values.
I agree with my colleagues. Good literature transcends time because it reveals truth about human nature, something that does not change over time. The Great Gatsby has no healthy, enduring relationships in it--not between families and certainly not between spouses. (The only possible exception is Nick's relationship with his family; however, they are not a factor in the story.) Because the relationships between poor people and rich people are both failures, we learn what matters in a relationship is clearly not money. Because both rich people and poor people demonstrate bad character, we learn that money does not determine character. These were truths in the Jazz Age and they are still truths today.
In my opinion (and considering the well-know relation of The Great Gatsby to Fitzgerald's own sad life), I think that Fitzgerald was trying to send a message that wealth and power, ... even in the context of bootlegging (in the case of Gatsby) and good writing (in the case of Fitzgerald), can not buy you either happiness or love. Both Gatsby and Fitzgerald tried. Both Gatsby and Fitzgerald failed. If Gatsby had succeeded, he'd be with Daisy living happily ever after in the end. If Fitzgerald had succeeded (as some who mistakenly think his marriage to Zelda proves), then he wouldn't have turned to drink to drown his troubles or continue to frantically prove himself through great writing (that he had already achieved) until his dying day.
Fitzgerald's message is not limited to the Jazz Age. The shallowness and materialism and hedonism of this period serves as a historical example of the destructiveness of selfish behavior in a civilization. Greed is always responsible for the destruction of a civilization. Are there not examples of this truth today?
I don't think Fitzgerald's message is one that applies only to the time period in which he wrote. I think that he is saying that there are many people (in any day and age) who only care about others for their money. I think that he is saying that people like Daisy only want material things and do not really have mature and unselfish emotions. I do not think that Fitzgerald foresaw the crash of the economy. I think he was simply reflecting on people's general selfishness and greed.
I think that Fitzgerald is speaking to the basic idea that the time period of the 1920s was doomed to failure in the manner it cultivated relationships between people. Fitzgerald understood "the Jazz Age" as one where people used others as means to ends as opposed to ends in of themselves. So many characters "use" people for their own self interest in Fitzgerald's work that it becomes almost an accepted conclusion that the time period will invariably result in a "crash" of intense proportions. Jordan Baker, Tom and Daisy, Myrtle, and even Gatsby himself are all guilty of seeking people out for not their own values but rather what they come to represent. Even Nick is guilty of doing this, as well. In the end, the characters lack any real sense of social solidarity and human compassion as they seek the next "swanky" party, or the latest piece of salacious gossip. In depicting relationships in this manner, Fitzgerald is making a statement about how any social context that carries on in this manner is bound for ruin of massive proportions. The Great Depression that follows the party of the 1920s comes then as no large surprise.