@Liquidxlax The god's aren't trying to do anything. Their world's, mana is lacking, Earth's mana is both saturated and completely untouched. People sent from Earth only have one role: Live in the world they're sent to. Do as they please. Their very existence acts as a wedge that allows Earth's unused useless mana to leak into the mana deficient world that houses people who actually use magic. Anything that happens to the otherworlder is completely up to their own choice. Normal people just live as they please, die, and have their soul enter the cycle of reincarnation. Saint wants to wipe out all diseases? She uses god power, faith of the masses, and the entirety of her soul to do it. That's her own choice.
and in the first place, it's not really considered improving the world when medical knowledge gets forever lost in the process.
Kufo only told Ryouma about little miss saint as a topic of conversation. You're reading too much into it. The only divine beings who want to actively harm people for their own self interests are the god of fishing (non-malicious), and demon kings.