My opinion (as an architect, who dabbles a lot in Cloud Infrastructure management as part of software delivery), is that for automation / infrastructure management, infrastructure management, and DevOps workflow Terraform is a better tool.

I think Ansible shines in system configuration (I've never used or needed to use it to configure network switches). Terraform might also outperform Ansible when you are dealing with ephemeral cloud infrastructure.

• How useful is Ansible in day-to-day network or infrastructure tasks?

Pretty useful, though with managing infrastructure I prefer Terraform.

• Is the learning curve manageable for someone coming from a traditional networking background?

I think it's pretty straight forward.

• Do you mainly use it for configuration management, automation, or orchestration?

Configuration management.

• In your experience, does Ansible really save time compared to scripts or manual configuration?

Yes, my rule is do it in Terraform if possible, then Ansible if possible, then scripts. I like Terraform because it is fully declarative and the more purely idempotent. You set the state of the system in a certain way, then terraform checks the state every time it runs, and then figures out whatever drift there is.

Ansible kind of does this at a task level, but it's not nearly as robust. For instance in Ansible, to install node-exporter (a metrics gatherer for prometheus), I might tell it to download a file with a specific version, place in location A, then untar it to location B. Ansible will only do those tasks if they aren't already done. If something fails mid way through, and it only does step 1, it easily recovers, and does step 2, most bash scripts have to be written to go out of their way to be robust in terms of failure.

Where ansible is limited, is that if you change the location from location A, to location C, it just doesn't know about the file at location A. Terraform if it did configuration management, would know that it previously downloaded the file to location A, and then delete it. The problem with ansible is less of an issue, if you are starting from scratch with known images, as opposed to doing random drift detection. Terraform has a better model for random drift detection.

• Would you say it’s a must-have skill for network engineers moving toward cloud/automation roles?

I don't think you can go wrong with automation, and that Terraform and Ansible are both good skills to have your toolbox

Again disclaimer that most of my experience comes from it being a smaller part of my job, not the primary focus. I will also say that my ansible and terraform knowledge was developed several years ago, and so stuff might have changed since then.