I honestly think you're mistaken in your comments about PlanetSlade's format, Jack, and here's why:
The feature pages on the site each run to about 1,000 words, or roughly the length of a full newspaper feature. Include the box copy, and Hattie Carroll's 13 pages add up to about 18,000 words in all, or enough to fill 72 pages of the average paperback book. That's a hell of a lot of copy to present in one single lump and, even on-line, I think most people would find it very unwieldy.
In my view, the change you suggest would actually make each article harder to read, harder to navigate your way around and far less appealing as a reading experience. After all it's not that hard just to click the little number at the bottom of each page when you're done, now is it? Especially as the numbers guide bolds up the page you're currently on as a convenient reminder. A thousand words per page is considerably more than the "driblet" of information you imply, and I don't think it's unreasonable to ask people to turn a page after that amount of copy.
The format as it stands divides the site's content first into three category headings - Murder Ballads, Secret London and Miscellany - each of which is colour-coded throughout. Within that, there's the individual features, each clearly identified in every page's headline, complete with periodic section headings to provide a breather when you need one. Where there's a tangental topic I want to cover that doesn't fit within the main feature, it goes in one of the boxes where people can read it later if they choose. I'm sure it's not perfect, but that does seem like a reasonably logical structure to me.
You ascribe the popularity of the "pages" format purely to advertising demands, but it may have just as much to do with the fact that magazines like The New Yorker clearly find it a good way to make their on-line content accessible to readers. I'm sorry you found some aspects of the site difficult to use, but unless I get a LOT more evidence that this is a widespread view, I'm afraid PlanetSlade will be staying exactly as it is.