Text Content Distribution
The content within pages of any website can vary a lot. From very small sections of text on a highly pictorial home page, to larger volumes on pages explaining the finer details of a product or service.
Fortunately, Google regards individual pages separately for individual rank capability, topical classification and so on, so each page can obtain its own ranking position to a large degree.
However, pages are also judged by the company they keep, and where their links come from.
In an example site with 20 poor quality pages and 1 great quality page, the internal navigation of the site will connect the poor pages to the one great page – meaning internal links are passing little or no credit, and may count as 20 negative votes for the good page.
In an ideal situation, there will be many good pages interlinking and sharing topical relationships between them.
Pages should still have their own focused topic based on a one or two keywords, but topics on other pages linking to each other with closest proximity should have some semantic connection. Websites that contain information on vastly different topics should have a system of categorisation where topically related pages carry a greater number of links between them than do pages of different topics. This will signal that the categorisation operates as a cell within a larger structure, and that pages within each cell cast positive linking ‘votes’ for each other, but less so to other pages outside the cell. To achieve this effect, content has to exist in sufficient volume on many pages.
Again, I expect the SEO value of categorised structures to be genre dependent.