[Quoth]

There was High Fantasy before and after Tolkien. There was and are loads of British & Irish fantasy writing from Victorian era till now.
Not all fantasy that might be termed High Fantasy is like Tolkien and maybe the worst are the attempts to badly imitate elements by people with no background or understanding of the Mythos and stories of the past that Tolkien mined.

I've no doubt that Lester and the Del Rey publishing helped popularise certain kinds of fantasy in the USA, that's probably good. But the article is a bit hyperbolic and ignores elsewhere.