I'm not that familiar with nihilism, but I'm rather surprised that "humans have to give it meaning" is part of the core. That's somewhat non-obvious to me; intuitively I would have expected nihilists to believe that meaning cannot exist.
Can you point me toward some sources that say nihilists actually believe that humans are capable of creating meaning?
That's a big part of existentialism (Sartre, Camus, etc), in which life has no inherent meaning, and it's rather empty existence, and it's up to the person to make any meaning for themselves.
- Nietzsche in Thus Spoke Zarathustra
what marks humans out from the rest of the meaningless universe that suddenly blesses them as meaning bearers? almost seems to imply some sort of religious idea that humans are not a part of the ubiverse
Now whether that those answers are accurate is a different question. But I think it's clear that humans crave meaning, and are happy to relegate meaning-making to third party institutions such as organized religion or the media.
Just a good-enough-for-you meaning.
>almost seems to imply some sort of religious idea that humans are not a part of the ubiverse
Well, they're not like other parts, in that they have meta-cognition, and a lot of it.
Planets and black holes and ants don't wonder about meaning.
Non-human subjective experiencers also imagine meaningful objects in their own minds. There's nothing special about humans other than their ability to communicate with other humans.