Trying Firefox again after many years on Chrome. As a developer, this is the thing I'm missing most so far.

Have been using the Allow-Control-Allow-Origin: * extension[1] on Chrome, while not perfect, is tolerable.

1. https://chrome.google.com/webstore/detail/allow-control-allo...

I agree, although obviously it needs to be smart about how widely it disables. There was an addon available but it got removed from addons.mozilla.org I assume because it violated security. The developer still hosts the addon though.