Hi there,
I too experience a issue when launching Sims 3 from within the Origin launcher application.
I was playing around with the actual Sims 3 application on my external hard drive from my backup before upgrading from Sierra to High Sierra.. anyhow long story short, I managed to open the Sims 3 launcher via the Sims 3 application, and it stated there was a patch available, and after patching the Sims 3 the game works, opens and plays on High Sierra.
Here is a url for the patch - https://bluebellflora.com/sims-3-manual-super-patch-for-mac-1-67/ - there are few versions depending on where you live, and if you Sims 3 game was disc or digital based. The patch version I ended up with is 1.67.2.024017 being digital for my game.
It will require a extractor application which are available on the apple app store for free. The webpage url I have mentioned has detailed instructions and links to the files, so see what happens. Also if it does work, make sure you make a copy of the patch file for future use and just in case.
I don't think it's a new patch, more of a super patch - but this worked for me. So short answer, yes Sims 3 works with High Sierra - just a rather muddly and picky application which needs patching and some jolly patience to do so.
After you have done the patching as stated above, login to Origin, and start/play sims 3 to launch.
Let me know how it goes. If it doesn't work, I really do apologise, but happy to keep helping. But this is from my experience only, and worked for me getting Sims 3 to work on High Sierra Mac OS.
Cheers,
Rebekah.