teieuw It's not officially supported, but you can delete the folder for any given pack you don't want to use. Each one has a folder directly inside [install location]\The Sims 4. The folders inside Delta only hold patch data, so you can ignore those.
In order to delete one of these folders, you'll need to close the EA App and kill the EABackgroundService in the Task Manager. Disable automatic updates within the App as well, or it might try to reinstall the missing pack(s). You can of course cancel the download if you catch it in time.
If the App still tries to install your packs, there's a more involved workaround; let me know if you need it.
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