I worked with the Dagger team on that. It was super hard to marry two DAG engines that work in opposite directions. The team eventually heard from users they wanted to write in the language of their choice, so there are now a bunch of SDKs.

I think one could wrap the Go SDK with CUE, and have oft considered doing it, but the work has not migrated from the backlog yet. I've been toying with a CUE powered monorepo DX CLI that is more akin to BuildPacks, using Dagger as the containerization layer.