Edit – Origin is now working since the release of El Capitan Public Beta 5.
… And you know why? Because as of today, the 3rd August 2015, El Capitan is still in beta. This means that you are participating in the beta program at your own risk as the operating system is not fully stable yet. That’s why it’s called beta. No 3rd party apps are officially supported in El Capitan because the final release is not available yet. So if you encounter a bug in any Apps that are not Apple’s, tough. However if you do encounter a bug in the operating system and Apple’s Apps, be a dear and report them via the Feedback Assistant.
So if you only have one Mac, and you are not particularly clued up on how beta programs work, I have one question for you – why
the fuck on earth did you enrol in the beta program in the first place? Because you wanted to be one of the first to have El Capitan on your Mac? Well more fool you.
Lunder89 over on the official Sims forum has posted this super video showing detailed and easy to follow instructions on how to get Origin to work properly in El Capitan:
It involves Terminal, installing Xcode and downloading and installing Homebrew. Good luck.