"...pretend they don't exist or don't matter."
That's a truly disturbing possibility, but one sadly in keeping with some aspects of human behaviour.
I completely agree with your last assertion: if ET takes enough time to get acquainted with humanity before attempting contact, I can easily imagine them deciding to take a pass on us. (*take* a pass, not *make* a pass!)
In the cosmic family, we'd probably be the psychotic cousin on whom no one wants to turn their back ("creators in the sky," and all that). Better, perhaps, to simply let us languish in the belief that the family doesn't exist.