The crucial difference is that CD postulates that if a change passes your automated test suite, it's good enough to immediately go live. I've dealt with many complex systems, some with pretty exhaustive test coverage, and this wasn't true in any of them. Unless your service is completely brain-dead simple (which none of them are once you have to scale), you always need a human looking at the release and driving it, and turning things off if tests missed bugs.
And last I checked their jobs aren't, in fact, automated. They just moved to the various cloud providers and were renamed to "SRE", with a major boost in pay.
