The author asks: “Who decided that the American public couldn’t handle ‘a soft and fitful luster’?”. I'm gonna go out on a limb and say the correct answer to that question is “research”. Linguists and child psychologists have studied the effect of dictionary definitions on learning and realized that simpler definitions are more useful to school students than the author's dream of “stuff that sings”, and that a clear and succinct definition like “a quality that evokes pity or sadness” is more comprehensible, and hence more useful, than whatever Webster's blurb is trying to express.
It should be ironic that the author would use “fustian” as his prime example — a word which, prior to reading this article, I had never encountered before, but after seeing the paraphrasing, “It’s using fancy language where fancy language isn’t called for”, I now know exactly how to describe this piece.
The modern (english) dictionary aims to serve as a list of definitions and meanings of words for someone who requires a list of definitions of words. This means that the explanations and example usages have to be short and simple because the person using it may not have a full command of the language.
The original Websters dictionary, as far as I can tell, serves to document the language for existing native-language users. This lets it be more expressive in the words definition (because you can use more expressive language), with the expectation that the user of the dictionary already has some sort of mastery with the language.
Nicely put. Sums up entire paragraphs worth of information in a single simple sentence that effectively conveys the idea.