It's a great book. I'm not sure I agree with the reasoning of the article; I do think there's a "hope" element to it but at the same time, there's a "the rich are not to be admired" element to it which, 7 years into the Depression, has to have meant something.
It's also evocative. The book transports you to its time and place, and that time and place is where good people suffer amidst the trappings of extreme wealth and bad people wander through, oblivious to their good fortune.
Brett Easton Ellis' Less Than Zero owes more than a little bit to Gatsby. The difference is Fitzgerald knew how to write, while Ellis was barely out of high school and bitter as fuck.