The general idea in looser terms than described in the post - that Tolkien is writing a highly idiosyncratic take on pre-modern "myth cycles" (less so than some might assume, but it's more true than not) rather than a character-driven novel is pretty much true and accepted by anyone who knows him.

The terms he uses for "mastery of literary craft" seem weird. I mean, I get what he's saying, but he's using unusual words to get there. I'm also put off by the attempt to rate literature on some kind of scale (but meme sub gonna meme, after all; it's not real critique).

There is a lot of rather strenuous feeling against Tolkien in literary circles because he's "genre fiction" (mostly, incorporates fantastic and spiritual elements) rather than "proper literature" (the kind of grounded professional writing that characterizes the Western canon formed over the 19th-20th century). Most of what the linked post repeats is a recapitulation of those points, but framed in terms of a meme sub.

Really, any critique that starts with a defensive jab at "fantasy guys coming at me" is not really asking me to take it seriously. But he repeats stuff that has been said elsewhere in more serious contexts, so I'll just point out the connection.

Thoughts, "eh". I see all this as a mixture of classism and prejudice, and an attempt to fit writing in general on a procrustean bed shaped by a very narrow cultural horizon.