“Good prose is like a windowpane”
The gaps one discovers in one’s education. Isaac Asimov wrote an essay comparing writing like a plate glass window versus writing like a stained glass window, taking the simile to the extent of pointing out that clear plate glass is actually the more difficult technology, and was the much later development. I was very impressed by this essay in my youth. I grew less so as my reading broadened. I had always assumed the simile was his own, but he undoubtedly borrowed it from Orwell.
As for the substance of the claim, I am currently going through a William Faulkner phase. Am I to take his prose as being bad?
As for that clear-glass prose, when I first got a Kindle I went through a cycle of re-reading old favorites from my early adulthood: books that I certainly would have considered to be of the clear-glass rather than the stained-glass prose style. Reading them today, I often find the prose instantly recognizably dated. Perhaps the simile should not be clear glass, but clear plastic that yellows as it ages.