After reading the reviews I think it is important to point out that premise of the show is that the male die-off was limited to mammals, not every living kind of creature.
I think that it is quite obvious why this series was a bomb.
The viewers didn't expect, or want, to see a world devoid of males, which tend to be men, to be such a disaster.
Nobody knew how to run power plants, sewage systems, railroads, oil refineries, chemical plants, etc. It made it look like modern women depended on men for most of the niceties of 21st century life.
Had there been another season society might have stabilized into an eighteenth century agricultural/Amish-like situation, but without the likelihood of children what would have been the point.
I think people were expecting something more akin to "The Handmaiden's Tale" and not a series about why women need to be more involved in STEM.