I’d add Poul Anderson to the list as well as all those mentioned in the article and by the commenters. He was as influential to fantasy writers as Tolkien and drew from the same well of memory, mythology and faery & folk tales. I have a book of essays by prominent fantasy writers about Middle Earth and Tolkien’s worlds that is dedicated to Poul Anderson. I reread it every couple of years to remind myself why I love the genre.
Grandfathers of Fantasy
Everything Is Better With Dragons 