We did. Each action can be written in the language of your choice (I personally use bash) then wrapped in a declarative CUE config (typically quite short).

Then you compose declaratively in cue.

Here is an example of a package to deploy to netlify: https://github.com/dagger/dagger/tree/main/pkg/universe.dagg...

Have you heard of or explored https://github.com/aws/constructs (related: https://github.com/aws/jsii and https://github.com/aws/aws-cdk)?

This is what CDK uses for declarative modeling, but gives the opportunity to use languages/tooling that most devs are already familiar with. CDK8s already uses it as a replacement for yaml (technically, the yaml becomes an implementation detail rather than actually replaced)