Terraform is a massive improvement over Ansible if you do anything non-trivial; even if it sucks, it sucks significantly less than Ansible at managing infrastructure resources.

I sometimes fool myself into thinking I can use Ansible in simple cases and that Terraform would be overkill but so far I've regretted those decisions every time.

Ansible wasn't designed for IaC, but configuration management, and even at that wasn't the best tool.

What made it popular was that it was easiest to start with, but that's pretty much all of its strength compared to the competition.

Ansible is sort of bad at everything, and does a few things decently.

I use it as an orchestrator / clusterssh replacement, but for configuration management it makes me nervous because I can't trust it to just not break for stupid reasons.

Last time I used it on Amazon Linux 2 with packer. It worked, but 1/3 of the time it failed with some strange error about yum database corruption.

I suspect what was happening is that Amazon Linux on start run yum to apply all available updates, and ansible was not respect yum locks, which is very surprising given that Ansible came from Red Hat so they should have known how important locking is for yum.

I ended up using salt (which has its own set of issues) and never looked back.

One big difference here is that while the tools might all depend on the SDK provided by the cloud, the tools themselves can also do a whole lot of good/wrong on their side. Terraform fixes a lot of that by delivering a 'standard' provider interface with normalised data formats, resource structures and encapsulation. That was pretty much a requirement for the tool to work anyway, otherwise it wouldn't have a unified way to check for configuration drift, plan changes, apply changes, do cleanups etc. You also wouldn't be able to pass data around easily (you'd end up shuffling strings around instead).

Some people prefer to do the CDK thing where you use a general programming language to synthesise the IaC stuff and then run it that way, but that doesn't really fix anything because a CDK is just built on top of the same SDK. As an added insult to injury, you now don't have a domain-specific language so save you from yourself (and your team) with all the anti-patterns you now have at your disposal ;-)