For the World That Was Lost

[Inspired by Delicious in Dungeon, Isekai Shura, Fullmetal Alchemist, and Goblin's Cave] There are very few people left who know exactly what happened three hundred years ago. The world has lost too much, but no one can say what, exactly, has been lost. All anyone knows is that human technology has made no significant progress in three hundred years. Dwarves are timid and avoid trouble, hiding underground; many half-elves have fallen into lives of prostitution; halflings spend all day complaining; goblins are nearly extinct; goblins are narrow-minded and fanatical; dragons desire nothing; and the sea folk will never sing again... Three hundred years have passed, and the world seems better on the surface, but it's still a complete mess.