The story does reveal the hypocrisies of the socially successful people in the story, but I don't think one can make a sweeping generalization that all socially successful people are hypocrites. That said, in this story, the Ansleys and the Slades are both rich and successful New York families. They are people that belong to the good country clubs, that live in posh New York City apartment buildings, and that can afford to travel abroad every year. Grace's husband was a successful stockbroker, Alida's a successful lawyer. With her lawyer husband, Alida globe-trotted around the world. However, in spite of this success, she harbored a very ugly jealousy all of these years. She suspected that her husband was more in love with her friend Grace, back in the day, and she lived with that memory her entire life. She never told anyone, she did not tell her friend, but she kept it inside. She acted like everything was just fine, so in this way, she was a hypocrite. She is also hypocritical in her interaction with her friend in this story. In the beginning, she is friendly, recalling old memories, sitting with her friend, discussing their daughters, etc., and this is phony, because she really is jealous of Grace. Gradually, as the story unfolds, she reveals her true nature.
We can surmise that the husbands were hypocrites as well because we learn that Grace hastily married Horace two months after she and Alida returned from Rome. So, Grace must have been pregnant. Surely Delphin knew about the pregnancy, and he never said anything, all those years. So he was a hypocrite. And Horace married Grace, then she has a baby 7 months later? Surely he knew the truth, and yet the two families lived next door to each other and were part of the same social set for all these years.