Jason Ridpath's poem starts with a puzzle about identity. If something is labelled by a labeller, then who labels the labeller? The speaker's answer is that you need another labeller, and then another, and the chain never ends. So the opening claim, that you can't be what you are because it can't be labelled, is really about how any fixed definition of a self keeps slipping away.
After that, the tone shifts. The speaker lists ways people usually settle the question: choose your own label, hand the choice to destiny, follow the stars. These come across as options offered almost casually, with no real conviction behind any of them. The last line, "Let your environment chew you up," is the bleakest and most surprising. It suggests that if labels can't hold, the world will shape you anyway.
The mood is dry, detached and a little unsettling. The speaker sounds less angry than weary, as if giving up on self-definition is both a relief and a loss.