This isn't quite accurate. It won't uninstall or remove things that a previous version put into place, unless you explicitly remove them before installing them as part of your playbooks/roles.
Exactly. This whole "declare your environment" thing with Ansible doesn't work.
I've completely mixed experiences with Ansible. Yes, it's easy to get started, but it's certainly annoying having to create playbooks for removing stuff to get a clean state.
To be frank, my experience with configuration management has been a mix between "YES! THIS IS WHAT WE NEED!" and "...but it still doesn't adhere to immutable states." That's been true with Chef, Puppet, and Ansible, for me. I haven't experimented with other techs.
Depends how you write your playbooks/roles. You can write a role that will both add and remove depending on the value of a variable in your inventory. Then tweak the inventory and re-run.
I've completely mixed experiences with Ansible. Yes, it's easy to get started, but it's certainly annoying having to create playbooks for removing stuff to get a clean state.