This horrifically written document alleges that CI tools are risky because if they fall they grant a vector to other parts of infrastructure. That's also true for just about any machine... even a developer laptop.
Good CI/CD processes increase not only security (less crufty servers lying around) but also recovery procedures because they force you to be able to deploy... to new, external, backup or refreshed infrastructure, if necessary.
This talk is written in a Black Hat idiom: take trendy technology, perform basic risk assessment, find one or more exploitable software security mistakes, generate "catchy" title.
It's unlikely that the author really believes CI tools are so risky that you should avoid them. On the other hand, it's good to know that your CI infrastructure is part of your attack surface; chances are, the author came up with the idea for this talk after exploiting a CI system on a real pentest (I know that happened at Matasano a couple times).
Good CI/CD processes increase not only security (less crufty servers lying around) but also recovery procedures because they force you to be able to deploy... to new, external, backup or refreshed infrastructure, if necessary.