How does Fitzgerald demonstrate the ideas of the Modernist period in The Great Gatsby?

Fitzgerald's work represents Modernism in a variety of
ways.  The most profound of these is that there is a completely tragic ending. 
Modernism was animated with the spirit of depicting tragic conditions in all aspects of
life.  The fact that Gatsby dies at the end, his death goes unpunished, and that the
real criminals in the story continue and actually prosper are all Modernist tendencies. 
There is a stunning rebuke of the idea that justice and morality end up forming the
structure of consciousness.  At the same time, Modernism was concerned with exploring
the tragic and more bleak side of what was commonly associated with positive and
redeeming values.  In this instance, it is the ability to dream.  Gatsby is a character
that believes in the authenticity of his dreams, and of appropriating the world in
accordance to his own subjectivity.  His failure and death represents the crushing
weight of such dreams, and how consciousness is a desire for the garden resulting in the
painful and forced embrace of the desert.  While wealth and advances in being "modern"
were present, nothing could shield Gatsby from such a painful
end.