"Shut down" is a little deceptive:

"Google announced that GWO as a separate product would be retired as of 1 August 2012, and its functionality would be integrated into Google Analytics as Google Analytics Content Experiments."

They just merged it into another product, where it still exists today: https://support.google.com/analytics/answer/1745152?hl=en

I wonder how is this Google Optimize different from what's available in GA today.