If your CC/Mods aren’t loading in-game, and you have checked that the CC/Mods are properly installed, it is most likely the same reason as saves not loading, your iCloud Drive settings are pushing data to iCloud because your internal storage is full and you have Optimise Mac Storage enabled in System Preferences > Apple ID/iCloud.
Older documents will be stored only in iCloud when space is needed. If your internal storage is getting full it doesn’t matter how many files you keep adding to the Mods/Saves folder, the older files will be stored only in iCloud where the game cannot access them. If you keep adding files it will in fact push more files to the cloud.
To get round this you need to either disable the Optimise Mac Storage setting or, if you are feeling brave, use a symlink to redirect your Sims 4 folder to an external drive.
Remember CC/Mods must also:
- be enabled in the in-game options
- Be unzipped (unless the creator dictates otherwise) in .package or .ts4script format
- be placed directly in the Mods folder