That's maybe the theory, but in reality, the only thing Ansible hopefully is, is idempotent between playbook runs - but there are no guarantees there, at all. Only in very simple setups things can be fully declarative in it's totality.

Don't have much puppet experience, but I can't count the times anymore that I've had to add steps to playbooks just to determine stuff used in one of the following steps. The other option was to write a snowflake Ansible module. The individual steps/plays might be declarative, the playbooks are not.

They look declarative but every Ansible playbook I have ever read or written has involved some imperative code. And even if you only use it in a declarative fashion, it doesn't change the fact that it's very much a step-by-step ordered list of things to install.

The declarative syntax is certainly a step up from shell scripts, but it's not as pure as K8s.

Ansible is only declerative on a action level. At a playbook level it's imperative. You can install and remove the same package within a playbook, the outcome will be dependent on the order.

Puppet is fully declerative but for me it lacks an easy way to undo changes. It would be nice if it could work like Terraform where it keeps a 'state' of all changes it made in the past so when you remove a resource from your config it could 'undo' the change.

I still use Puppet (mostly with Bolt nowadays) for systems that don't fit Kubernetes, but they're becomming less and less.