The author seems to think configuration management is about installing packages. That's something the package subsystem does, with a reasonably mature handling

The author seems to think configuration management is about installing packages. That's something the package subsystem does, with a reasonably mature handling of dependencies too. That makes it look like a glorified shell script. (Which may be a case of when all you've got is a hammer everything looks like a nail.) But configuration management concerns centralized management (hence "management") of decentralized systems. It can answer questions such as "why is this sceduled job running on nodes of type x but not y and who put it there?", and guarantees such as "application w and z are always in lock step concerning parameter p". I've seen organizations move to containers, and they all inevitably end up with more and more containers and increasing complexity. Centralized configuration management is more important in that environment, not less. Modern tools such as Ansible and Puppet have grown up in a devops worls and have good support for managing containers (even if they are a bit of a moving target) and there is no reason to be scared of them.