Started a new world in survival mode with hard difficulty selected. Built a skeleton farm, but after killing hundreds of skeletons not a single one would drop a bow or piece of armor. They only drop bones and arrows. Loaded an older world (survival mode, hard difficulty) and updated it to 1.21.4 and had the same results using diamond sword with looting III. Other settings I use are disabled fire update and I have one vanilla tweaks datapack which is prevent endermen greifing.