Why can't humans do it too?

[Current World: No Game No Life Zero (Completed) - A Comprehensive World of Various Yokai (Completed). Actually, you only need to read the first volume; the rest are up to you.]
[This book contains no tragedies; the author favors happy endings. Not having read the original novel won't affect your reading experience.]
War, plague, famine, countless natural disasters—the earliest people, carrying torches, struggled along the rugged path of civilization. But Suer never imagined that one day he would be struggling under an even more terrifying despair, desperately trying to survive...
The ceaseless war between the divine race and their creations, the planet's surface being relentlessly altered like an oil painting, the entire world marching towards death...
Even humans themselves have this question—why do humans still exist?
as well as,
Why can't humans do it too?
With these questions in mind, Suer's long journey has only just begun...
[If you're bad at summarizing, please read the plot.]