Kulturkampf

[Besticus Maximus]

that kind of sounds like tolkien establishing canon rather than the claim that there's no canon

if you write a book about a dude saving the world and then you write a sequel where you reveal the events of the first book never happened and it was all in his head in a mental institution, that's canon, it doesn't mean you get to pick and choose and say the first book really happened in that universe

It's more that the ideas were constantly in flux. Originally gandalf was just a wizard who helped Frodo, by the end he's a special kind of angel because reasons with differences in what he's meant to be from book to book.

Also consider that Tolkien was ostensibly a scholar of anglo saxon and nordic literature, the tradition he's writing from has no idea of canon and there are various versions of every story.