In further confirmation that it is a man's world, a signed urinal from 1917 was voted the most influencial piece of art of all time.
I love art history and have undertaken a modern art avocational study for the last few years, to the point that I do understand and appreciate the movement (no pun intended :) Further, I studied pre-modern art history for real while working on my Master's, so I sincerely appreciate the formal study of art history, too.
Following is the way I see Duchamp's urinal. I have two points I haven't seen elsewhere per se...
1) As a point of comparison with something most people understand, whereas Impressionism was about replicating the momentary fleeting glimpse of a scene/feeling/gesture/light, modern art is more focused on the intention rather than the outcome.
Hence, the hunk of porcelain isn't a mere urinal any longer, b/c the artist declares that it is now art. "I intend this urinal to be art!," pronounces Duchamp. "So be it!"
And so it is.
2) As a result, the Duchamp's urinal piece is highly influencial, b/c it removed art from the canvas (or other conventional medium) and absolutely plopped it down into the mundane.
Although art is construed to be rather hoity toity, progressive artists have always struggled to make art closer, more real, more relational, more banal, even. The removal of the superficial gloss or veneer is the goal of true art, not dressing it up.
There are many examples, but I will cover only a few. This "dressing down" phenomenon happened in the Renaissance and other transitional times when art dared to go beyond the sacred (with only church or mythological subjects represented) and attempted to portray the secular, the commonplace. Think about Dutch genre paintings like those of Hals and Steen, with lively family scenes, full of revelry, noise, and community. (This style is my favorite.)
Or consider all those Impressionists rejected yearly by The (uppity and traditional French) Salon; they dared to paint relaxed, playful scenes and strayed into the ill-respected landscape. Lastly, ponder the edginess of Goya and Picasso who insisted upon dramatically portraying the horrors of war; their paintings were statements relevant to both their peers and their leaders.
Removing the gloss, all of these paintings are of the things of life, of existence, and of the world, truly the "Reality TV" of old.
Art is about bucking the system, not about being lofty. Status quo is ever passe. Adapting to a bucked system just means there's a new movement to be rejected and remade.
For future reference, I think the most influencial piece of art for the post-post-post-post-modern era should be the female urinal. I'm an artist. I'll be glad to sign it. We deserve equal time.