Sims 3 64 bit on Mac keeps freezing yet can still play in background

@jazzmiint  You may have posted the specs of your Mac before, but please post them again: everything under About This Mac except for the serial number.  Please also list the packs you currently have installed.

Sure, here they are:

macOS Big Sur Version 11.5.1

MacBook Pro (13-inch, 2020, Two Thunderbolt 3 ports)

Processor: 1.4 GHz Quad-Core Intel Core i5

Memory: 8 GB 2133 MHz LPDDR3

Graphics: Intel Iris Plus Graphics 645 1536 MB

And the expansion and stuff packs I have installed:

Late Night                                Movie Stuff

Ambitions                                 70s, 80s, 90s Stuff

Pets                                         High-End Loft Stuff 

Showtime                                 Master Suite Stuff 

Supernatural                             Fast Lane Stuff

Generations

Island Paradise

University Life

Seasons

@jazzmiint  The Pets expansion causes a lot of problems on hardware like yours.  In your specific case, the issue might be Pets alone or in combination with Bridgeport, but it's easy enough to test.  In either Applications or Users > your username > Applications, you'll see a folder labeled "The Sims 3 Packs," inside of which will be a folder for each pack you've installed.  Move the EP05 (Pets was the fifth expansion released) folder to the desktop, and you've uninstalled Pets.

Unfortunately, a save that's been played with an expansion present cannot usually run properly when that expansion is removed.  But what you can do is try playing a new save in Bridgeport without Pets installed; if it runs well for a while, Pets was probably the issue.  If it runs poorly, try playing without Pets in Sunset Valley, which is a better-made world than Bridgeport.  You can also try playing with Pets in Sunset Valley, or in Appaloosa Plains: the routing for pets is best there.

The point is, you might need to experiment a bit to see whether you can get the game running smoothly.  And please keep in mind that saves can run well for a few sim-days and only have issues later, for various reasons.  For example, the problems might start after a number of households adopt pets, or after a sufficient number of strays have spawned.

I tried removing the Sims 3 Pets expansion and starting a new Bridgeport game, I got in roughly 5 minutes of gameplay (even that might be a stretch) and it froze again. I then proceeded to try Sunset Valley without Pets installed and during the Sunset Valley world loading screen, it started flickering but the green loading bar was still going up, the flickering wouldn't stop and eventually I had to force quit as it just wouldn't stop or finish loading the world. I'm starting to think maybe Pets isn't the issue? I'm not sure what else it could be, perhaps my MacBook simply isn't strong enough to play the game despite being able to play Sims 4 smooth enough. I'm no expert do you think there is something else that could be the issue?

@jazzmiint  Your Mac's hardware isn't all that powerful, but a number of people are able to play on this laptop or similar ones.  Others have the same experience as you're describing.  I'm not really sure what the difference is, especially considering how standardized the builds are and that the simple explanations (heat, other apps running in the background) haven't been a problem for at least some affected people.

Anyway, you can try to cover everything all at once.  First of all, put the laptop on a hard flat surface (like a desk) so it will be able to cool itself properly.  Restart the computer, and don't open any apps.  Move the Sims 3 folder in Documents > Electronic Arts to the desktop.  Sign into Origin and put it in offline mode, then disable the laptop's wifi so you're entirely offline.  Launch the game, load a new save in Sunset Valley, and see how it runs.  Don't change any of the graphics settings other than the resolution, and for good measure, disable the interactive loading screens.  (The setting is under the third or fourth Options tab.)

If this doesn't work, try the same except in a new admin user account on your Mac.  This shouldn't affect graphics or anything else you've described, but it's worth trying just in case.

Please let me know whether your laptop seems to be getting too hot.  it should get warm, and the fans should run, but Sims 3 isn't demanding enough to push the processor to its limits.

@jazzmiint  Strange, I can always see my game library even with Origin in offline mode.  If it's not working like that for you, that suggests that something else weird is going on with Origin.

Regardless, you should be able to launch Sims 3 directly from its .app in either Applications or Users > your username > Applications.  It should work both if Origin is already running and if it isn't: in the latter case, you'd see the Origin sign-in window, but once you input your credentials, the game should load.

I seemed to somehow fix seeing my games in offline mode of Origin, yet when clicking play and opening the Sims 3 Launcher I am met with this message (in the screenshot below) and when I click the play button, it takes me out of the launcher back into the Sims 3 page in my game library where the option to open the launcher is. If that makes sense. I also tried on a different admin user and got the same issue 5 minutes into the game, no change in graphics or any settings (aside from removing the interactive loading screens which I usually have off anyway) and still had the frozen game but the option to click around in the background. 

@jazzmiint  The error is unsurprising given that the launcher tries to load ads and other data from the internet.  But that shouldn't prevent the game from launching at all.

If the game is still working in the new user account, try turning all the graphics settings down to the lowest options.  (Change the settings at the Main Menu, then quit to desktop before loading a save.)  I don't think you necessarily need to play like that; the point is to see whether you can get things stable and then build from there.

Going by the launcher in your screenshot, it looks like Pets is still active.  The pack shouldn't prevent the game from launching either, but it certainly could cause the freezes.