Question

Would it have been better if Prometheus never came and gave the people fire? Was humanity better off because it had fire and civilization, or worse off because the cost was misery and disease?

Answer 1

They were better off. Without the discovery of the uses of fire, mankind would not be here. Fire led to the rapid increase of newer, more advanced tech, such as a sword instead of a club.

Answer 2

According to the myth, Prometheus gave the people fire against the wishes of the gods. The gods, in retaliation, punished the people by sending them misery and disease. It is difficult to say whether this was a convenient bargain. However, it most likely was, as fire allowed people to be warm and cook food, thus fulfilling some of the most basic needs of human beings.