I don't think the blame is on people experimenting with steer. If the project was successful and steer isn't harmful, they'd have a way to fight against cancer.
Just like how the story portrays, humans make mistakes and some are downright evil. But a lot of them aren't and we're all trying out here. Most species have to get rid of the sick or disabled because they wouldn't be able to survive. But we overcame that through trials and errors; or as you've worded it, playing with nature.
I think what we can take away from the story isn't that humans are bad or foolish, but that nature will take its course because it's random. But that randomness is perfection and it's all but a cycle of life and death.
You make a great point, i guess this shows the limit of our knowledge as well. Sometimes we just dont know we are doing something bad for the greater good.
Mc couldve lived normally if people arent so foolish to play with nature. This all started with the scientists experimenting with the steer and it shows how far humans have come to selfishly achieve something. Mc didnt come into conclusion with this hatred so easily, he keeps repeating that this is an accumulation of the past deaths he experienced in which he highlights that deaths involved humans was mostly is a result of selfishness. Sure the rule of the jungle is survival of the fittest and he understands that fully, but he had come to realize that this character of humans, the evil, is something unnatural which causes disorder in this world and is affecting nature.
However what makes this story good is that in the end, despite his intervention, he realizes that he also causes disruption in the world. In being human himself, he realized that humans still have good in them and thats what stops the evil although not perfectly. There is still balance in the world. So the best conclusion is that he cannot coexist with humans as he causes more disruption to what should naturally happened.
Tho him being the world is a little lame for me lmao But thinking about it, maybe he is the consciousness of the world, and this is a journey on how he slowly come into knowing what the world is becoming.