Stuck on second loading screen sims 3

HeyITOG22​  Try disabling Advanced Rendering (if it's enabled), enabling object hiding, and turning all the graphics settings to the minimum.  Do so at the Main Menu, then quit to desktop before trying to load a save.  And when you get back to the Main Menu, make sure the changes stuck.  (I know the issue with settings reverting was in Windows, but I want to make sure.)  Start that save in Sunset Valley.

If this doesn't help, would you be open to installing an older version of macOS?  While Tahoe is compatible with the Mac I believe you have (MBP 2020, 13", i5-1038NG7... although I should really have confirmed), the OS only supports a few Intel Macs.  Plus, this particular model had issues rendering Sims 3 in the past, although I don't think I saw any reports that weren't due to other issues past Catalina/Big Sur.

Point is, it's entirely possible that the graphics driver in Tahoe works with your Mac for the most part but not in Sims 3 or with the technology it uses.  Since Sequoia is very recent, any other apps you want to use should still be compatible, but if you want to install Store or custom content through the launcher, you'll need to go back to Sonoma.  (There's an issue with the newest version of Sequoia and with Tahoe where the launcher crashes if you even view the Downloads tab.)  Given everything else you've tried, I think it might be the next logical step IF you don't have a specific reason you need to be running Tahoe.