We were targetting configurations of Concourse for deploying software. We would have to do essentially the same deployment to multiple environments (dev, qa, staging, performance, prod) and Concourse doesn't provide a sufficiently rich configuration in its use of yaml. For a single app cut and paste is acceptable but once you get into multiple microservices, it becomes more efficient to do it this way.

Have you looked into Jsonnet/CUE/Dhall? They attempt to solve this problem, but give you an actual programming language instead. I've been using Jsonnet to successfully escape the 'yaml-templating-yaml' hell for years now.

But yeah, concourse configuration files are probably the worst YAML verbosity offenders, even worse than k8s manifests.