Here you setreturnvalue in a loot table mixin. That stops all other mixins from other mods from working. I assume you just want to add your loot, so you can just do

ci.getReturnValue().addAll(event.itemsToAddToDrop);

That way my mod will also be able to add items to a loot table with your mod loaded.

Idk if you still support 1.20.1 but this should be a quick fix