Humans aren't precious because there's like 8 billion of us. 300 years ago it was probably more like 600-700 million (highest estimates around a billion) and it took more humans to achieve less work.
Under capitalism, more people means cheaper workforce because more competition between workers. Individual worker is valued less. Under communism you don't put a dollar figure on a human the same way, but they're still more expendable when you can just get another one to do the same job.
I'm not advocating for mass genocide or eugenics, I'm just saying that's how it is and we better get used to it. Things are precious when they're scarce. We're not scarce.