they definitely exist but they’ve never visited human civilization

I specify human civilization because I think it’s possible that aliens may have visited our planet before human civilization but that their visit was so long ago that it is impossible to tell the evidence of it from random noise - like imagine if a space probe was in our orbit at some point a million years ago, I don’t think there’s any way that we would be able to tell, and declaring it to be true or untrue one way or the other is kind of a Russell’s teapot situation.