I feel that all warning are doomed. If we discovered some ancient site (let alone ancient alien site), each marking would prompt us to dig further and explore m

I feel that all warning are doomed. If we discovered some ancient site (let alone ancient alien site), each marking would prompt us to dig further and explore more. No warning works (even if an explicit one), when met with a curious being. See: Eve and the Tree of Knowledge (from Genesis) or Pandora and her box. And when the beings are not curious, it is unlikely that they would develop technology, or be tempted to new, alien places.