Continuing my reading of Meyer Schapiro ("The value of modern art" (1948) in Worldview in Painting: Art and Society),
Schapiro acknowledged the heterogeneity of early- and mid-century visual arts. But he went on to apply a broader view of its commonalities. “However, if we consider the art of our time – and I speak only of that art which is fresh and original and could not have been done in a previous age – I believe it is possible to discover in it certain features that set it apart from the work of preceding times” [134; emphasis added]. Citing claims that modern art does not have subject matter, Schapiro asserted “in the art of the last fifty or seventy-five years [before his 1948 presentation], types of subject matter that are sufficiently standard and characteristic” :
1) direct observations of everyday life
2) the life and work of the artist
3) “the consciousness of art itself: [paintings in which] the constituting elements do not form images or signs for objects, but are themselves ideal figures of elementary operations in the shaping of things; these, too, are an important subject matter of art, drawn from art itself” 
4) “the interior world of the artist,” expressed through non-representational composition of color, line, shape, and/or brush strokes.
Schapiro compared these themes to those of earlier periods of Western painting. “If the art of the Middle Ages is about supernatural beings whom one never saw directly or in ordinary vision, if the art of the Renaissance is about mythological and historical figures, and if the art of the Baroque period is rich in moral and political allegories, then the art of the last seventy-five years is about ourselves” .
If modern artists are individualistic, and face no art-world limitations on subject matter, why was there, up to Schapiro’s writing, so little reference to human inequality and suffering in modern art? Schapiro turned to this question at the end of his essay or lecture, and gave it too short a treatment. He glossed over the paintings emphasizing the horrors of twentieth-century war, for example. He suggested that modern artists’ reliance on individual patrons and purchases disciplined them to emphasize themes of leisure or related to pleasure.