I don't blame YAML for Helm's approach. I'm also not anti-templating, but templating the DSL as a string, and manually setting the indentation level strikes me

I don't blame YAML for Helm's approach. I'm also not anti-templating, but templating the DSL as a string, and manually setting the indentation level strikes me as a particularly hacky approach. Compare with something like https://jsonnet.org/ https://jsonnet.org/ (no endorsement), which let's you do the same kind of substitution, but directly in the structure of the data.