Rome.
It fell to barbarian hordes, as the more technologically advanced Romans fell into excessive comfort, pleasure, and decadence.
They were gluttonous (they used a feather so they could have a second feast) and they exposed babies to die if the father didn't accept them. Their entertainment was watching people get killed by lions in the "games", etc. They pursued raw pleasure in all its base forms.
They used prophylactics, and ɧoɱosɛҳųαƖity was endemic as well.
Sound familiar?