The poem opens with a worried question: where are we headed? The speaker pictures people "sailing in a coffin," a grim image of drifting toward death, or else dreaming of anchoring beside a rainbow, which is a pretty fantasy with nothing solid behind it. Both options look like dead ends. The "gold and purple ashes" suggest that something once glorious has burned out, and the speaker says these remains can't bring back the phoenixes, those mythical birds that rise from fire. Old stories of rebirth, in other words, won't rescue us.
The second stanza turns practical. Instead of waiting for a miracle, we need to "recoup the elements' balance," which sounds like a call to repair our relationship with nature. We must "create new suns and moons" to light the cave and start again. The mood moves from anxious and bleak to determined, even hopeful. The speaker doesn't trust myth or daydreams, but believes real effort could still make a fresh future possible.