Tags don't get added to blocks or items unless all supported mods are loaded.
Need to either find a way to add conditions to these, or load tags another way

Maybe try separating the different mods into different sets of brackets, then add a line that says: "required": false

Example from the Elytra Slot Mod.
{ "replace": false, "values": [ "minecraft:elytra", { "id": "silentgear:elytra", "required": false } ] }

On a side note, I wonder if this is what causes the problem I'm having in Issue #28.

EDIT: After testing with some modified tag files to fit the above example, I can confirm that this is not causing the problem in #28.