Your function is probably getting overwritten by the default collections addon, considering that addon is loaded on demand. If you want to overwrite a function that doesn't exist yet, you need to declare a required dependency in your TOC file first. You want your addon to be loaded
after Blizzard_Collections:
Lua Code:
## RequiredDeps: Blizzard_Collections
I should also mention that generally speaking, replacing official code instead of hooking it is dangerous territory. You can easily spread taint this way, because as soon as your code changes a value on something that is then traced in the execution path to a secure action, you'll get the big ugly blocked action popup.