I agree somewhat with the proposition that YAML is annoying for configuring something like a workflow engine (CI systems) or Kubernetes. But having it defined in YAML is actually preferable in an enterprise context. It makes it trivial to run something like OPA policy against the configuration so that enterprise standards and governance can be enforced.

When something is written in a real programming language (that doesn't just compile down to YAML or some other data format), this becomes much more challenging. What should you do in that case? Attempt to parse the configuration into an AST and operate over the AST? But in many programming languages, the AST can become arbitrarily complex. Behavior can be implemented in such a way as to make it difficult to discover or introspect.

Of course, YAML can also become difficult to parse too. If the system consuming the YAML supports in-band signalling -- i.e. proprietary non-YAML directives -- then you would need to first normalize the YAML using that system to interpret and expand those signals. But in principal, that's still at least more tractable than trying to parse an AST.