@rellietay I hope when you manually deleted everything, you followed a guide like this one by Bluebellflora:
https://bluebellflora.com/how-to-do-a-clean-uninstall-and-reinstall-on-a-mac/
If not, it's best to clean out those hidden library files before installing any packs, or you may well get another pile of unknown errors. But once the base game is installed and patched using the Super Patch, if you can launch the game, you've dodged that issue. (Don't use the launcher to patch; it often does a less than thorough job.). By the way, the Super Patch needs to be run on the base game icon in Applications, not its folder or the icon for another pack. You can download the digital region version here:
https://bluebellflora.com/sims-3-manual-super-patch-for-mac-1-67/
If for some reason the patched base game won't launch, even after a manual uninstall, you can uninstall again, create a new admin user on your Mac, and install into that account. This will remove the hidden library files from play.
Aside from the incompatible graphics issue that it sounds like you don't have, unknown errors have two other causes. Both are due to certain packs—Ambitions, Late Night, Fast Lane, and Outdoor Living—not installing correctly. The first issue is that these packs likely don't have their own aliases in Applications, alongside those for the base game and your other packs. But you can create them manually:
https://bluebellflora.com/sims-3-packs-not-showing-as-installed/
The second issue is that files from these four problem packs don't get copied into the folder for your newest pack by the date EA released them; in your case, that would be Island Paradise. So you'll need to copy those files yourself, for both Ambitions and Late Night. The video guide in this post shows you exactly what to do:
https://answers.ea.com/t5/The-Sims-Mac/CURRENT-ISSUE-Sims-3-Unknown-Error-in-El-Capitan-Sierra-High/m-p/5725514#M5926
If you do all this, you should be fine. Bluebellflora's guides are the source of almost all of our information about how to install and play TS3 in Mac OS. But if you do happen to have trouble, feel free to ask for more help.
P.S. The world of Isla Paradiso is so poorly made that it's almost unplayable, even though the other content of the pack is fine. Before playing in that world, you may want to read @ciane's thread on fixing IP. You can follow her instructions to edit the world yourself, or you can download her fixed version and play it forward.
https://forums.thesims.com/en_US/discussion/811253/removing-ip-lag
