If this animal died, these citizens might still be dark and gloomy with the memory of death, not the memory of their liberation. The entire community takes pills to suppress their emotions, they would never have known heartbreak, they wouldn't even know what it's like to love someone and then lose them. Jonas' parents, for example, put their two personalities into a system, analyzed them, and then combined them. They don't like each other or even have feelings for each other, they just respect each other and share two children, but that's it. Not experiencing grief, death, pain, or depression can be a good thing in many cases, but pain and sadness are how people mature throughout life and become more capable than before.