saultrixter It's worth testing without iCloud Drive syncing any data because saves can get large, particularly when the sims travel to other worlds. If you don't want to change the iCloud settings, taking the computer offline will of course also prevent syncing in the moment. You can sign into the EA App and put it in offline mode, then disable wifi before pressing Play.
If that doesn't help, is there any particular action that causes the crashes? I can test on my Mac to see whether it happens for me as well. For example, in Windows, my game always freezes for a few seconds, but doesn't crash, when a staircase is revealed in a tomb. I haven't tried exploring in macOS though, and I haven't seen any reports of specific places in WA worlds being an issue.