A Web Page is a Unit of Business Intent
The natural way to think about a planning a website is in terms of groups (or sections) of content. Information Architecture principles help us do that by organizing content into logical groups.
But the sitebuilding user interface of Drupal does not let us easily build IA spaces in that natural way. In this video I go into a bit more detail about the ways around this problem in Drupal 7 (and this mostly applies to Drupal 8 as well).
It all gets down to this problem: how do we define a 'web page?'
As a Content Management System (CMS), Drupal has a pretty clear answer to this question. But it's not one that supports a semantic process for building out an Information Architecture. At the end of this video I offer my own answer which is based on an Outside-In perspective.