Adding to this × what @hadley mentioned re. roxygen2 and README, one of the things that impacts ease of use is consistency across sources of documentation. I think that's part of the goal of pkgdown (right?!)
As a user, one of the most frustrating feelings is:
"I know I saw how to do this, but now I don't know where it is!" 
- Part of this is about vocabulary (beginner's curse/curse of expertise): reference, articles, and news are all words that people have heard before, but not necessarily in this context. I think this is similar to some of what's being discussed in
Building foundational skills for programming beginners - #5 by jennybryan - Part is consistency across sources vis-a-vis navigation. For example, DiagrammeR has gorgeous documentation…and I always have like twelve tabs of its docs open when I use it, because the elements of it feel like they're in different places in the docs, versus the GitHub README, versus docs within docs for GraphViz and Mermaid (e.g. I often want, but don't remember where the attribute styling is).
I'm a big fan of cross-referencing, and/but I don't know if this is pedagogically sound, or even actually useful to most people in developing a mental framework around a package, or concept (my thinking could probably benefit from a good dose of @jennybryan -style rectangling). There's also the challenge of dealing with various media/space constraints that might make this more or less practical.
In fact, now I'm not sure of whether this comment fits squarely in this thread re. docs, or fundamentals (@jessemaegan, I feel like this might be a learning how to learn thing).