macOS unable to open any non-Apple application

You've got to be kidding me. When Apple's servers are down, all Macs worldwide start freezing randomly? My XCode is hanging during builds, is this why?

This code signing enforcement stuff has gone way too far. Heads should roll for this.

Almost certainly so. Apple has built chains of certificate trust very deep into the OS, along with apparently an assumption that this particular revocation service check is reliable & fast enough to call out to the network a lot.

Oh man, imagining a DDOS to fail that over.

Imagine how many people would lost their productiveness, maybe not at the big corps or govt (I assume they use a version of mac that call somewhere else/don't). But very very many people.