@taenbro Even one bad custom content item can preven the game from launching. You can try removing your cc, but that might not work if it's installed through the launcher. Instead, try playing in a clean user folder. Move the entire Sims 3 folder out of Documents > Electronic Arts and onto your desktop, and when you open the launcher, if it opens, a clean folder will spawn with no content. Don't add anything to it yet; just make sure you can get far enough to start a new save.
If that works, you can start moving your content from the old Sims 3 folder to the new one. I'd suggest testing your new cc first to figure out what the problem is, that is if you want to use any of it. By installing it into a clean folder, you can safely test the items one or a few at a time, then discard the entire folder if you run into trouble and create yet another new one.
Once you have your cc sorted out, you can add the rest of the content you'd like to keep. Here's a description of the data in your user folder so you know what you might want to transfer:
https://sims3.crinrict.com/en/2011/01/faq-user-files.html
If you can't open the launcher even after moving the existing Sims 3 folder, please first make sure that the folder moved and didn't just copy, and check both the local Documents folder and the one in OneDrive (if you use it) for another folder that might also need to be moved or renamed. If that's not the issue either, please run a dxdiag and attach it to a post.
https://help.ea.com/en/help/pc/how-to-gather-dxdiag-information/
