That only the Hobbit and LotR should be considered canon is not a hot take. Lukewarm take, at best.
However, the idea that The Silmarillion is a work by Christopher is... not really supported by the history, imho. It is a work finished by Christopher. So maybe it is by JRR and C. But it isn't like Christopher Tolkien was working from bare notes or outlines - his father had worked on The Silmarillion longer than LotR. He'd submitted prior versions for publishing. He left copious materials, and Chistopher was specifically trying to fill out his father's vision, not using it as a vehicle for his own creativity and expression.
Did JRR have issues with the work up to the 1950s? Yes. Did Christopher have to fill in chunks? Yes. But that doesn't mean Christopher should be given primary credit on the work.
This, I can agree with.
If you talk about it strictly canon, you could say that yes...only the Works published by J.R.R. Tolkien are the Middle Earth Canon.
HOWEVER...if we go with author's intent it can open up a bigger can of worms...
Inclusive of Author's Intent...
What others miss as well is that Christopher was ALSO the one of the first to read and APPROVE of what was written about Middle Earth that was published. He was also the primary approval factor in regards to what eventually was written and came out.
He was ALSO one of the PRIMARY AUDIENCES that it was actually written for PRIOR AND BEFORE anyone else.
If anyone would know the mind of his father, it was probably Christopher.
There is no real analogy regarding this in regards to Star Wars or many other worlds, though with Lucas I would hazard that Lucas had several different types of Canon, with HIS being the PRIMARY Canon which....yes...would ONLY include the movies and the other item he stated were HIS canon (which, ironically puts the Radio Dramas ABOVE anything Disney or others have called Canon). He ALSO approved other types of Canon, with the Novels being secondary, but NOT HIS canon...but canon regarding approval from him and HAVING HIS INPUT and DIRECTION at some points.
Lucas and Star Wars is a BAD comparison to LotR as far as Canon is concerned...or so I would feel. Better something similar where supposedly canon works were written after the author's death but had items inclusive of the authors writing or intentions. It's hard to find an exact match, but there may be some works which have similarities in their composition.
In that way, the closest we could say to Canon would be The Wheel of Time series. The last three books were NOT written by Jordan.
Just as Christopher is somewhat the holder of the works of his father (or was before he died) and the designated heir of it to determine what or what was or was not part of the Canon...you could say Jordan did something very close to that.
He did not write the series initially primarily for Brandon Sanderson, nor did he have Sanderson proof everything and anything he would publish first...BUT...he did have extensive notes he gave to family and gave them the collective okay to continue the world with those notes. IN that light, Sanderson would be the collective HEIR as you would say to continue the series of the Wheel of Time (which he did).
I would probably consider the Silmarillion and some of the later works (of which Christopher Tolkien normally made abundantly clear in the Middle Earth series of his which was an extensive book series that there were many versions, sometimes which he wrote and compared, even when they conflicted) as well as the trilogy of other books (Children of Hurin..etc) as much Canon as the last three books in the Wheel of Time series.
Is it by the same author.
No.
Thus, it cannot be as specifically Canon as anything written by the author. If we want to stick with PURE author's writing and intent, it can ONLY be what the author or creator themselves created.
If we go by what the author or creator INTENDED...then it is possible both what Christopher Tolkien put out as well as what Brandon Sanderson put out to be seen as an extended Canon written under the auspices of the original Author's intent.
In either case, Disney Star Wars would still not qualify under Canon in that light.
Does Canon Matter?
For some...yes.
Why?
Because they respect the author and the author's intent.
The REAL controversial thing I have is...
For those who don't respect authors and like and/or like to pirate things then obviously no, it doesn't matter. They can call it whatever they want...their head canon, their personal canon...etc....but as the author's intent and writing (and why the author's universe even matters that much to them to spend money and time on it in that case...who knows) it doesn't matter...only the big corporations and Billionaires making money off of the author's works later matter.
So, they make excuses on why the author is worthless, the author's ideas and thoughts on the matter are worthless, and why the corporations should get thousands if not millions of dollars to rip off the ideas of the author. If things go the exact or say the exact opposite of what the author wanted...these types of people don't care. They would hate the author if they could because the author isn't the billion dollar corporation...and in these types of people's minds the only thing that really matters is the RICH getting richer by using others ideas and tossing the authors wishes by the wayside.
People who actually RESPECT the author and the author's intent are getting few and far between these days. They'd rather spend money to a rich corp than to the author any day of the week.
NOW THAT is an unpopular opinion in many places these days...or so I find.
However, as an author who has had material stolen by others and the BIG corporate machine...that's MY hot take on the entire 'Canon' idea.