It too is declarative. It too can be easily extended. It's also something a lot of people already know.
I used to use Ansible or Puppet for these things before Terraform was all the rage. It was a lot more stable than trying to distributing those state files, which is a strange design to pick. There are plenty of existing modules but it's also dead simple to write your own.
It should be noted that the article is written to sell services for Terraform. It is unfortunately built on a few false premises that are never argued. Very few Chef developers would agree with Chef being somehow more imperative than Puppet, for example, seeing how the language was originally thought of as a superset of Puppet's.
The author does not specify which module is used for AWS, but it is not representative for how one would want to use Ansible for infrastructure. Writing idempotent playbooks is widely regarded as best practice in the Ansible community.
I have used Ansible for declaring node state in large production environments (not some dinky startup) and found it to be a very straightforward way to manage infrastructure.
I understand that mitchellh himself personally created a bunch of cloud modules for terraform at the beginning, and those were likely of higher quality than whatever created by some internal developers assigned by Google/Microsoft, and might be slightly better than the AWS modules maintained by community.
Anyway, when it comes to ansible versus terraform, we shall move the discourse to states management instead. With ansible, you don't have to deal with states, but will need to clean up the cloud resources separately. With terraform, you can use the tool to clean up the cloud resources easily, but then you also have the headache of managing states. Plus, whenever you change something, there is always the nagging feeling that it will do a destroy/recreate instead of an in-place update.
It too is declarative. It too can be easily extended. It's also something a lot of people already know.
I used to use Ansible or Puppet for these things before Terraform was all the rage. It was a lot more stable than trying to distributing those state files, which is a strange design to pick. There are plenty of existing modules but it's also dead simple to write your own.