Allusion, Allusion, Allusion
Sure, Yeats may be charting a new poetic territory in this poem (someone get this man a map of the heart), but that doesn't mean he avoids shout-outs to his old works. Poem and myth and plays all wrap into a description of all the things he's not doing anymore. We still have to read about it all, though.
Come to think of it, this sort of straightforward allusion isn't all that different from the sorts of allusions Yeats used to embed in his earlier works. He's always been fascinated with Celtic, Greek, and Indian mythology and, well, anything at all that involves gods and giants and beautiful women. Now, however, he points them out to cross them off his list. Sigh.