Minecraft wiki entry for Survival_with_no_enabled_data_packs, associated text: It was possible before 18w06a to trade with a cleric for gold ingots, but now it is no longer possible, as furnace recipes have been added to the vanilla data pack, instead of being hardcoded into the game, which causes all furnace recipes to be disabled when the vanilla data pack is disabled. As a result, gold ingots are now impossible to get. Rotten Flesh is impossible to get because mob drops are disabled without the vanilla data pack. Hence, all trading with clerics is now impossible.