FWIW, let me share my own fanciful notion of what I choose to call mystical existentialism.
It means to me that existence is absurd and meaningless unless redeemed
by faith in God.
If God is at the center of things, everything has value and meaning.
The Fire and the Rose are one.
The impression I form from my reading of Eliot's poetry is the poet viewed things in this perspective.
Prufrock and Gerontion, implicitly or explicitly, find the world absurd in its departure from God.
They are painfully aware of their own imperfections, even as they aspire for purity and perfection
that belongs to the Absolute.