"Il faut etre de sont temps!" (It is necessary to be of one's time!), as Baudelaire probably never said. That was a rallying cry of modern art for a century, even thousands of years ago when I was in art school.
Here's an artist who did just that, Richard Lindner. He was a big name in the art world 30 years ago. Now, he's fallen off the map. I haven't heard anything or read anything about him or his work in years. All I know is that he died about 10 years ago. His work now looks as dated as an old Peter Max poster. It belongs so much to a particular period of time.
As Oscar Wilde once said, the problem with being too modern is that you wake up one morning to find yourself old fashioned. That's another aspect of modernity with which we are still wrestling. Things change so completely and so fast that generations now seem to belong to completely different cultures alien from each other. It's easy to make too much of this. Generational conflicts go back to the Garden of Eden. But nowadays, an artist who's so plugged into the "zeitgeist" (whatever that is) has to reinvent herself as much as Madonna in order to stay current. Richard Lindner didn't. Perhaps old Ingres had a point after all.
I've always said that the acid test of art is familiarity. That's so hard now in an easily bored and quickly jaded consumer culture that prizes novelty and sensation above all. I notice that when the press does stories about art, it's usually either about sky high auction prices, or about some kind of quirky gimmick by some contemporary artist; the Last-Supper-Carved-In-A-Peach-Pit type thing.
If a work of art that we've known for years and years continues to look fresh, continues to yield new discoveries, and if people are still talking and arguing about it, then it's probably a successful work of art. If people are arguing about it decades and centuries later, then it's probably a great work of art.