Glad you mentioned how much we still don’t know about the ways dolphins communicate with each other. In the light of that example, perhaps it’s overly optimistic to think we’d be able to understand other technological beings thanks to “commonalities we can find between our knowledge base and theirs”? Even though dolphins don’t use machinery, they pursue the same fish through the same waters as humans do… If commonalities in knowledge about fish haven’t enabled us to understand dolphins, is it likely that commonalities in knowledge about elements would enable us to understand extraterrestrials?