As one with a lot of experience in reading, and none in writing, I would summarize my attitude towards appendices or in-story descriptions somewhat less absolutistic rather as an "and" than an "or".

I like appendices, if they give me additional background or overview. I don't like them, if I have to refer to them to (fully) understand the story.

In times of crisis it is of the utmost importance not to lose your head (Marie Antoinette)