Williamson is absolutely right. Since John W. Campbell took over Astounding back in the 1930s, science fiction has been a genre whose stories revolve around characters, not just Big Ideas and Big Gizmos. Writers who write like Clausewitz (who is damned difficult to read, BTW) are never going to make it out of the slush pile because they are all about the Big Idea of grand strategy. Yes, Orson Scott Card wrote about grand strategy in Ender's Game, but he didn't go on for 700 pages in a Germanic pedantic way about it; he told us the story of an alienated little boy trained for battle in zero-gee. And the same is true of Joe Haldeman, Robert Heinlein, John Scalzi, Gordon Dickson, David Drake, and all the rest of the great combat SF writers. They're all writing about people, and can't be arsed to write detailed treatises on military technology, tactics and strategy, because that sort of thing turns off a lot of the potential audience by taking time away from the characters.
Shit, I understand this and I've never had a syllable of SF published. What the hell is wrong with Andrew Liptak that he doesn't?