> Salt, Ansible, Puppet or Chef _could_ be used as part of this process, but so can shell scripts
I don't see the point of your post, and frankly sounds like nitpicking.
Ansible is a tool designed to execute scripts remotely through ssh on a collection of servers, and makes the job of writing those scripts trivially easy by a) offering a DSL to write those scripts as a workflow of idempotent operations, and b) offer a myriad of predefined tasks that you can simply add to your scripts and reuse.
Sure, you can write shell scripts to do the same thing. But that's a far lower level solution to a common problem, and one that is far hardsr and requires far more man*hours to implement and maintain.
With Ansible you only need to write a list of servers, ensure you can ssh into them, and write a high-level description of your workflow as idempotent tasks. It takes you literally a couple of minutes to pull this off. How much time would you take to do the same with your shell scripts?
As he mentioned, immutable images make those type of tools largely moot.