Final answer:
1920s authors such as Sinclair Lewis and F. Scott Fitzgerald criticized American society's middle-class superficiality and the upper class's hypocrisy.
Step-by-step explanation:
The 1920s authors critically depicted various flaws in American society through their writings. Two significant examples of these flaws are the stifling and shallow nature of middle-class life, and the hypocritical pretensions to rectitude by social elites. Sinclair Lewis highlighted the former in his works like 'Main Street' and 'Babbitt,' attacking the monotonous and materialistic lives of the American middle class. F. Scott Fitzgerald, through 'The Great Gatsby,' portrayed the latter, critiquing the ostentatious lifestyles and moral decay of the upper class during the Jazz Age. These authors, part of The Lost Generation, often felt alienated from society which they believed was steeped in materialism and devoid of deeper values.