The way agency relationships work in the publishing world, which is more or less accurately portrayed in the quotes, it's amazing the sector works at all. It's a damned miracle that anything original ever makes it through, really, since the publishers don't want to see any unrepresented work, but very few agents are willing to look at anything from an author that hasn't sold something major to a large publisher, which sets up a perfect Catch-22.
On top of that, neither agents nor publishers want to see an isolated magnum opus, they both want to be assured of high production (Which sounds like it may be part of this DUmmie's problem) so they can cash in on success in a continuing stream of product, so bringing them The Great American Novel is fruitless unless the author can promise to deliver another equal novel every six months to a year for six books or so, otherwise they won't touch it.
Though it does explain why so much of what actually gets printed is trendy copycat garbage by a few very highly prolific emos.