Of course Pulumi can do for loops, you're using a proper programming language.

I meant that I doubt that I could 'cp -a' on a whole deployment tree, and deploy the copy successfully without having to make any code changes.

Although thinking about it, I take it back. It may be possible with Pulumi with the right code structure and naming conventions, and if configuration were separated entirely from the codebase, and if variables were inferred from the directory structure. That is really the thing that allows me do to it.

Yes, sorry for the rather pithy response, but separating out the "what changes" vs. "what doesn't" (config vs. code in your terms) is what makes these things possible.

As you also noted, doing this in plain terraform is kind of a pain, so using a tool like Hiera allows you to skip a lot of the work involved in doing it the "right" way. IMO if you're starting greenfield Pulumi (or CDK, anything that lets you use a "real" programming language) allows you to write (or consume!) that config in basically any form, instead of needing to funnel everything through a Terraform data provider.