Re: Sims 3 only runs without custom content, but I don't have any custom content.
@ayyyeden Did you ever have any cc or mods? And if so, did you delete your cache files after removing them? Did you uninstall simpack content from the launcher and/or remove the associated .dbc files from DCCache? It's also a good idea to delete everything from DCBackup except for the ccmerged.package file.
Regardless of what you've done so far, you can try pulling your TS3 folder out of Documents and onto your desktop. When you launch the game again, a clean folder will spawn with no content, third-party or otherwise. If you load a fresh game a couple of times and don't get this message, you can move your existing saves from the old folder into the new one, along with your .ebc files from your DCCache folder. (These files contain store content, if you have any, and can become corrupt, in which case it's often better to trash them and reinstall store content from scratch.)