Did you read the parent in haste or did they edit their post? They said:
> [1] It means that civilizations should exist that are millions of years more technologically advanced than us;
> [2] and should be leaving telltale signatures across the sky that we'd likely have detected by now.
> [3] And the absence of those signs would be relatively strong evidence that life, while common, isn't long-lived.
> [4]Suggesting that our demise too, will come before too long.
So they were talking about the great filter, not alien invasions, which is what you appear to be replying to.