I've solved half of the mystery of Saint John of the Cross. I'd always assumed that he was always a canonical figure, but he was not. I've found a dissertation (Recepción de la obra literaria de San Juan de la Cruz en España : (siglos XVII, XVIII Y XIX) / Antonio José Mialdea Baena) that shows that he hardly registered at all in literary terms and only enters the literary canon in the late 19th century with Menéndez Pelayo. So he wasn't a figure influencing any of the baroque poets, and was even more eclipsed in 18th century poetics. This explains why he isn't translated into English earlier.
For Lorca, Salinas, Guillén, Borges, Gelman, Valente, Colinas, maybe Cardenal too, he, not Góngora, is the supreme poet of the language. Probably for JRJ too. So we have to figure out how this happened. They were born into a world in which he had just become canonical, but they were still concerned with reading him outside the purely Carmelite context.
Valente complains about the secularized readings of this mystic poet. Guillén and Dámaso Alonso want to read him as an erotic poet, decontextualizing him completely. Yet wasn't this secular reading necessary just in order to make him mainly a figure of interest within the context of Catholic contemplative practices? We might remember that Pope John Paul II wrote his dissertation on this figure, in Rome in 1949 or so, but hardly mentions anything to do with the poetic qualities of the text, as far as I can tell.
Imagine if Neruda was one of the foremost Marxist philosophers of his day, and his poetry was almost an afterthought for 95% of readers. That reading his poetry presented a special problem of intentionality, trying to find a non-communist reading, etc...
The problem of mysticism is a false problem, I think, based on the mistaken idea that poetry takes an emotion in the poet and communicates it to the reader. It is only the reader who supplies the emotion, actually, in the sense that the poem cannot make me feel an emotion of which I am not already capable. Imagine the scary music in the horror movie. Does the film score composer have to feel that emotion first and then convey it to us? No. There is no need to think about the composer's emotions at all. We simply associate certain kinds of musical tension with certain emotions, and then these patterns have also become codified in the same way the open arpeggios of Western movies are codified for those landscapes. We might respond in many ways to a poem, laugh at a poem that is meant to be tragic, for example. Of course, we rebel when we are told what to feel too explicitly.
So we don't have to get into the mystic's head, recreate his experience. Our own heads are self-sufficient. The proof is that everyone recognizes his greatness as a poet almost immediately. It is immanent in the poems and we don't need all the commentary to do so. For most of us, the commentary gets in the way, of course. The idea that we should read the poems as though their author wasn't a mystic, of course, is profoundly off base, since it poses a false dichotomy between one theme and another: we are supposed to feel that everyone can identify with the love story, but only another mystic can feel mysticism.