The beta is no longer being used, and game updates added support for 2013 CPUs (AXV) to the Steam and GOG releases, and then 2010/2012 (SSE/SSE2).
Unfortunately, it is not possible currently to add support for older CPUs to the App Store release, and there is no estimate for when Apple may support the x86_64h architecture in the App Store (alternate executables need to be added to the app package so an appropriate instruction set can be used based on the system CPU).