I kinda liked the article myself. If one wants to approach Tolkien in a scholarly way, these items have to be considered. JRRT was sub-creating whole mythologies, complete with languages, and their own internal creation myths. A mighty big task for one man.
The problem comes when we, fans and scholars, try to see if all of his works fit together. I think Christopher Tolkien sent us down the garden path with his editing of the Silmarillion, where he used what was at hand to complete one of his father's universes. He gave us plenty of warning that it was a good-faith effort, but we shouldn't take it as gospel.
It's interesting how Tolien's successful "The Hobbit" brought a demand for more about hobbits. That, in turn, led him to use his Silmarillion universe, with modifications, as the setting for LOTR, with hobbits shoehorned in. Things grew and diverged, ("balrog wings"), and with the inclusion of material from "Unfinished Tales" guaranteed that no comprehensive canon could ever be agreed to.
I don't get upset about it. I look at all that material, and treat it like the fragments of ancient tales that have come down to us in various versions and fragments, giving us a tantalizing glimpse at a vast universe that we will never know clearly.
That's one way to look at it. One I have no trouble with. An easy way for me to consider it is to say that Tolkien worked on a single, great painting his entire life and portions of the canvas were reworked, repainted, added, or left out. The various notes Chris found reveal the canvas in stages. The published posthumous material attempts to show how the various layers of the painting relate to one another.
It's hard to say what kind of good a definitive canon for Tolkien would do. Fans would still ignore or critique the parts they don't like and filmmakers will simply rewrite it the way they want to anyway.
I think what Christopher has done with his father's notes is about the best we can hope for: an accumulation of the source material that will allow us to enjoy JRR's writing and invention as if we were to watch over his shoulder as he wrote it.
Which is why I enjoy The Silmarillion a great deal, even if it is not, in Mr. Martinez' opinion, "canonical: the wonder of JRR's invention and the splendour of his writing are still there for us to enjoy. That wonder and splendour are lost completely when Mr. Martinez tries to parse it for us to establish his canon.