I do not have the UC either, and I get the same crash notif here and there. From what I can tell, crashes aren't 100% unavoidable, but there are ways to make them less frequent.
I don't have too much experience with Sims 2 on Mac, so I will assume you're using Windows?
1. As others have mentioned before, apply and check the 4gb patch.
2. Fix your graphics settings, either manually or with Graphics Rules Maker. I prefer GRM, but some swear by doing it manually. Whatever works best. However, it is key that you use the correct settings. The wrong input for "Force Texture Memory" seems notorious for causing both graphical issues and crashing.
3. Obviously, CC and mods being improperly installed or uninstalled can cause crashing. I had an issue in which I did not completely remove a hefty gameplay mod, and that led to awful crashing.
4. I have found success by stopping all background processes not needed to run Sims 2... which is most of them that won't throw you an "access is denied" message when you attempt to stop them. Look into the standby memory fix - some of the problem applications might be difficult to avoid, but you'd be surprised at how much standby memory an app like "YourPhone" will eat up in the background. I always close all non-Microsoft applications.
As I mentioned before, I still get occasional crashing even after taking these steps, but it's usually on very large community lots after playing for multiple hours.