literally nothing can be changed or added, and there are lots of other posts listing this exact issue so im not sure what the deal is.

The file you listed literally can't be accessed at all and any edits simply don't take place. So im not sure how you are expecting people to edit this file

The file is located per-world in a datapack. Follow the tutorial here, and create the basic folder structure. Once you have the folder called data, create a folder at data/extra_tiers/item_attributes. You can put things in there.