Not sure how bad it could be given the hypothetical "millions of years more technologically advanced". They'd need to have a pretty good reason to care about us. Otherwise, we'd be so insignificant that it seems much more likely that whatever natural resources they'd want, would also be likely nearer and easier to obtain.
War-mongering, and otherwise zero-sum mentality shouldn't make all sense if they have the technology to actually reach us. [3-body spoiler warning] Kinda like in the Three Body Problem. It was kinda silly how advanced the Trisolarian were, while still bothering traveling to earth, rather than approach the problem in any number of more obvious ways
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.
in the book they couldn't stay in their system since it was unstable and our star was the closest to them and they knew we were less advanced than them.