“I think anybody who had been moderately competent, reasonably alert to the vitality of what was actually going on in the medium would have done the same thing I did,” he said several years ago. “I mean, the idea that Winogrand or Friedlander or Diane were somehow inventions of mine, I would regard, you know, as denigrating to them.”

John Szarkowski, 1925-2007.

I've posted excerpts from Szarkowski's essays here on more than one occasion.
His writings meant a lot to me.

Of all the enormously influential photographers that Szarkowski championed, William Eggleston seems to me the most vital. Pull him from the timeline, and the last thirty years of the medium really do collapse.
Hilton Kramer called William Eggleston's first one man show at the Museum of Modern Art (curated by Szarkowski) "perfectly banal" and "perfectly boring" (lazy, incurious remarks that are in fact, perfectly wrong.) The show, besides being shockingly good (to the point that it still looks contemporary 30 years later), was inarguably a major turning point in the history of the art form; a sudden, bewildering release from the predictable monochromatic poles of social-documentary moralism on one hand, and vacuous "zone-system" refinement on the other. Photography in the mid-70's (as practiced by people who referred to themselves as photographers, not 'artists using photography,') was dangerously close to a kind of formal calcification. William Eggleston, in effect, detonated the medium. And a lot of contemporary art photography is still operating in the chaotic, ear-ringing aftermath.
Legend has it that Ansel Adams himself sent a letter to Szarkowski protesting the hanging of Eggleston's pictures - irrefutable proof, if required, that Szarkowski was on the right track.

Here's Szarkowski's original introduction to Eggleston's first book of photographs, William Eggleston's Guide, published in 1976. Note the clean, lucid prose, the surplus of insight and ideas, and the absence of rarefied art jargon.