“The plain fact of the matter is that New York is much too good for New Yorkers” was written by American journalist Heywood Broun (1888-1939), from “I’ll Show You the City” in The New Republic on June 15, 1938. “Complete appreciation will come only when some Vesuvius has laid it low and posterity is forced to dig down into the dust to bring to light the buried treasure,” Broun continued.
   
   
Wikipedia: Heywood Broun   
Heywood Campbell Broun Jr. (/ˈbruːn/; December 7, 1888 – December 18, 1939) was an American journalist. He worked as a sportswriter, newspaper columnist, and editor in New York City. He founded the American Newspaper Guild, later known as The Newspaper Guild and now as The NewsGuild-CWA. Born in Brooklyn, New York, he is best remembered for his writing on social issues and his championing of the underdog. He believed that journalists could help right wrongs, especially social ills.
 
Google Books
Collected Edition of Heywood Broun
Compiled by Heywood Hale Broun
New York, NY: Harcourt, Brace and Company
1941
Pg. 451:
(From “I’ll Show You the City,” originally published in The New Republic on June 15, 1938.—ed.)
If you can keep body and soul apart, come rushing to the magical city. Lucinda, whether a job waits or not. But remember that Manhattan is also the place of sacrifice. It is only for those who can subsist on locusts and wild honey. In many respects is an American equivalent of Ceylon’s Isla and there be those who have been borne down by too much beauty and who walk through the canyons of the city as impervious to visual excitement as any pack mule. The plain fact of the matter is that New York is much too good for New Yorkers. Complete appreciation will come only when some Vesuvius has laid it low and posterity is forced to dig down into the dust to bring to light the buried treasure. If you have patience, Lucinda, it might not be a bad idea to postpone your trip to some such time when the guide, pausing in his patter to speak with deep emotion, may say, “And now beneath your foot, lady, is a crumbled stone which is all that is left to remind us that here the New Republic once functioned in offices which were considered very modern.”
 
Newspapers.com
30 October 1966, Chicago (IL) Tribune, Books Today, pg. 18, col. 1:
The Epic of New York City
HISTORY BY EDWARD ROBB ELLIS
Reviewed by Herbert Mitgang 
(...)
“The plain fact of the matter is that New York is much too good for New Yorkers,” Heywood Broun said. “Complete appreciation will come only when some Vesuvius has laid it low and posterity is forced to dig down into the dust to bring to light the buried treasures.”
   
Newspapers.com
18 November 1996, Daily News (New York, NY), “Rudy tales abridged too far” by Mike McAlary, pg. 17, col. 5:
The plain fact of the matter is that New York is much too good for New Yorkers.
Heywood Broun
   
Google Books
The Epic of New York City:
A Narrative History
By Edward Robb Ellis
New York, NY: Carroll & Graf
2005
Pg. 597:
Heywood Broun: “The plain fact of the matter is that New York is much too good for New Yorkers. Complete appreciation will come only when some Vesuvius has laid it low and posterity is forced to dig down into the dust to bring to light the buried treasure.”