That is correct; I've always found it a missed opportunity in Terraform. I still like it a lot as a tool.

A unified abstraction layer would certainly work for a subset of cloud offerings. Think the more basic stuff like EC2, VPCs, etc. Platform specific extensions could be handled as optional arguments to the unified objects.

That said, even though you need custom Terraform definitions for each cloud vendor, using one IaC tool still beats having to use a cloud-specific one for each of your deployments. The parent's point stands.

Learning terraform for the various providers = learning the different syntaxes and design philosophies of different python libraries.

Learning the different IaC tools for each provider = Learning Python, Javascript, and PHP.

Also, Terraform does state management and can be used to package deployments of apps to different platforms. Our IaC pipeline uses Terraform to deploy resources to AWS and several other cloud toolsets, all in one language.

The provisioners are the easy part - understanding the ecosystem and how the different parts of the cloud providers relate is the harder part. I routinely go back and forth between C#, Python and JavaScript using the official AWS SDKs and I understand how to accomplish what I need in either language. Using those same languages, I wouldn’t know where to start with Azure or GCP.

Using Terraform vs CF is easy compared to using AWS vs Azure.