Humans began to rapidly accumulate technological knowledge 600k years ago

Think of not only the replication crisis in science, but also the despair to retain "tacit knowledge" the failure of which often results in outright abandonment and outsourcing to somewhere else.

The technology to land on the Moon seems to be effectively lost. The supersonic airliner is for some reason not available either.

Same happened in Rome, and Rome itself together with Greece rediscovered civilization from a much darker age before them.

In light of that, the idea that any real knowledge could be retained for that long is preposterous.

The technology might be, but not the knowledge. The tech just became obsolete and probably not up to safety standards anyway. I doubt we'd have much trouble recreating a better equivalent if the incentives existed.