"Why, then, is [John] Marin so underappreciated by the art-world elite?"

Asks Terry Teachout:

The standard explanation is that even though he marched to the edge of abstraction, it seems never to have occurred to him to turn his back on the visible world. "The sea that I paint may not be the sea," he wrote, "but it is a sea — not an abstraction." After the rise of Abstract Expressionism in the 1940s, his deep-rooted belief in representation came to be seen as old-fashioned, even quaint.

But there may be a deeper reason. Americans have long had an equivocal relationship with their own art.... To this day there is a noticeable reluctance on the part of native-born art lovers to admit that a quintessentially American composer like Aaron Copland might actually be great, or that a stage actor need not have an English accent to perform the plays of Shakespeare or Stoppard. Could it be that the reputation of Mr. Marin, whose subject matter is as American as his briskly improvisational brushwork, suffers from our nagging sense of cultural inferiority?

I think Marin was originally overrated, and he's just not that good. Check out some images if you don't know the work.