Heya Muse Hill!
Hopefully late crit is better than no crit. I don't write a lot of verse, but I'll do my best to give you some feedback on the main points you brought up.
Vocab: I do think there's a good balance between common and uncommon words. Additionally, the words that are more uncommon are still recognizable - they gain interest, but aren't so out there you're left needing a dictionary to understand everything. That helps preserves the rhythm/flow of this piece, while still keeping the reader hooked.
Themes: For me, I see this about those who have had their history taken away from them, or are fighting to keep their history their own. When their voices are no longer loud, they wander through hidden texts and whispered words, getting around those that try to erase them, to keep their flame alive. The lines
No pious priest nor mission bell / Can long define our song
Till all the lineage of our past / Is full mythologised
What was that ancient tune? / How can the night bird's cry resound / With memories long gone?
Are really powerful and drive that theme across.
Rhythm: I'm not sure I can give great crit in this section, but I think it reads well/isn't pretentious in the slightest. I enjoyed reading it.
Hope that helps!
