I'm a highly literate reader and writer of technical topics, and there are a lot of bad technical writers who think they aren't. Except perhaps for the title, which is way too narrow, the article is excellent writing about a technical topic (which is quite different from technical writing)--but then I actually read it, so I know that he doesn't talk about a dichotomy between FP and systems, but rather between single programs and systems, and he explicitly says that his points aren't restricted to FP, but that because FP addresses the single program issues so well, FP programmers are particularly prone to missing the problem.