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.