The Macro Transcension Hypothesis holds that sufficiently advanced civilizations don't expand into space — they go the other direction, migrating computation into denser and denser substrates. The galaxy looks empty not because it is, but because its most advanced inhabitants have effectively become invisible to many forms of detection.
MTH doesn't require civilizations to be rare or hostile. It requires them to be efficient. As computation deepens, the optimal substrate shifts from stellar-scale megastructures to compact, cold, dense systems. The benefits of expanding outward diminish. The returns on going inward compound. At some threshold, the outward expansion stops — not because anything went wrong, but because it stopped making sense.
A transcended civilization isn't silent because it's hiding. It moved on. The era controls span roughly 50,000 light-years of a hypothetical galaxy arm; shifting them rebalances which civs are in which phase. The far-future result looks empty — but that's not the same thing as empty.
NGC 5139 — Omega Centauri — is 11–12 Gyr old. Any civilizations that arose there had billions of years to reach this threshold before our sun ignited. We may be looking in the right place — for traces of something that finished this arc long ago.