Carrot of Truth
War is Peace
I have actually read all the translated light novels for this series. As for the goblins they are regularly left unchecked because the world is constantly under seige from far worse things like demons liches hordes of undead dragons ect. Not really a good reason but the one presented regularly. As for the nonsensical amounts of glass and modern designs of structures I chalk that up to being easier to draw and the DnD inspired setting. As for the adventures guild the Japanese have an obsession with everything needing to be organized and official in their fiction.