I think that's true, but I would add that there's a third concept making its way onto the stage in V. As Virgil pointed out, religion is also being talked about here. Unlike in II, III, and IV where the speaker merely wonders about art and reality, the audience here demands something more than just creativity and truth. They want a replacement for "empty heaven and its hymns"--a poetry in which they can "take their place." These are spiritual and social needs that exist separately from truth and creativity. The guitarist's audience first claims that they no longer believe in the promises of Christian mythology. They don't want to hear about "the structure of vaults upon a point of light." This is an echo of the medieval belief in God as light and the church built upon that foundation. In Dante's
Paradiso, for example, God appears in a vision as a single point of light, and the identification of divinity as light was a pretty well established one by this point. The line about "torches wisping in the underground" also has parallels to Dante and the belief that the deceased live on as flames in darkened cavities beneath the Earth's surface. In V, though, this is all called into question. The audience considers this an antiquated mythology. They are now in the light--perhaps of reason--and don't acknowledge the church or God. They call upon the poet to fill that place: "Poetry/ exceeding music must take the place/ Of empty heaven and its hymns." The commentary on art and reality continues in V, but religion enters into the discussion, as well.
It is odd, though, that Stevens uses the word poetry to denote both an old mythology and a new art form. It's "greatness of poetry" that the audience doesn't believe in at the beginning and it's "Poetry/ Exceeding music" that "must take the place" at the end--a rather contradictory message. It's as though someone were saying "Don't talk to me of the deliciousness of maple syrup, but doesn't it go great with pancakes?" Stevens might be indicating that the audience wants a poetry that stands by itself and not one that relies on gods and religion, but it's an odd way he puts it. I suppose it could be there to characterize the audience as confused and self-contradictory. The first section of the poem make them look similarly confused.