I forget where I read this, but I have read that Tolkein was inspired by industrialisation and the destruction of nature when characterising Sauron, the orcs, post-fall Saruman, and the scouring of the Shire.
It takes Samwise Gamgee, a devoted and skilled gardener, spending a year of his life planting new trees to replace the ones that were lost.
Yes, he uses a magical resource he was given as part of his reforestation campaign, but it just speeds up the growth. The real factor is still Sam's tireless labor.
I was just being pedantic about the events of the narrative, because it's close to my heart.
Example: I write of a 'garden door opening' but what I really mean is 'penis-in-vagina intercourse'. Or I say 'anthill', but what it really means is 'urban sprawl'.
So no, there are no allegories in LotR; the One Ring doesn't really stand for the atom bomb or whatever.
- either "allegory" is meant to be a very strict one-to-one map, like Gandalf is really Jesus but has a different name in this story. Then the quote is irrelevant to almost discussion because nobody is trying to make such a point.
- or "allegory' is meant to be some loose inspiration, like the War of the Ring drawing from Tolkien's experiences in the Great War, the role of providence being similar in Catholic theology & in the legendarium, or more controversially the description of evil men or women being a product of its times. If such is the meaning of allegory, and Tolkien denied using it, then he is wrong.
I think Tolkien meant meaning 1. In either case it is irrelevant to most claims of some connection between a real word thing and a legendarium thing.