Some kinds of declarative automation are just bad. Case in point: configuration management. Ansible was written before we realized immutable infrastructure is

Some kinds of declarative automation are just bad. Case in point: configuration management. Ansible was written before we realized immutable infrastructure is the best way to go. Configuration Management tools craft system state dynamically like a drunk sculpting a Roman bust with a Louisville Slugger. You can get them to do what you want, but it takes a lot of work, and even then the outcome is uncertain. CM tools are often complex because a system whose state is constantly shifting requires complexity to handle it. If instead you make immutable artifacts, you don't need complexity. A simple series of straight-forward commands in a single version-controlled file does everything you need. Dockerfiles seem immature at first because of how simple they are, but in practice it's much more reliable than Ansible, not to mention easier to support. Thus, non-declarative automation, when used with immutable infrastructure as code, trumps declarative. Ansible is also only optionally declarative, which people miss just because it has that bastardized form of YAML for a config file. The simplest tasks, roles and playbooks work when executed sequentially, but not necessarily when out of sequential order. When you do make it super-duper-declarative, it can involve tons of confusing logic that makes it nearly impossible to understand, and is much more verbose (and complex) than a simple script. As soon as automation is more work and cost than the alternative, it should be ditched.