shakira-teehee I think I might have seen one other mention of the launcher crashing, but not taking down the game, in Tahoe, and that is not related to trying to install content through the launcher (its own separate issue). So I don't know of a fix. We've suspected that tighter security settings are the reason that people can't install content, and it could be that the same change is causing the crash in your case. If that's true, there isn't a fix or workaround.
What you could try is playing in a new admin account on your Mac. Don't link it to your Apple ID, and don't import any settings. Repair the game (EA App > Sims 3 > Manage > Repair) before trying to play.
The point is, if this helps, the trigger for the crashes is specific to your main account. If it helps once, perhaps the problem is a file being created in the user folder; maybe the launcher didn't crash the first time you played after clearing all your data, but only on subsequent tries? If the launcher crashes in the new account even the first time you try to play, the issue is global rather than limited to one account.