Launcher crashes when I open the downloads tab in Sims 3

bookwyrmthegreat​  I've merged your post with the master thread for this issue, which is a problem with macOS and not with your system.  There's a suggestion earlier in the thread for how to get around the issue with Store content, but it doesn't help with launcher-installed custom content.  For that though, if you still have your old data, even in the trash, you can restore the .dbc files in DCCache as well as any lots or households in Library that you might want to preserve.