I like YAML since anything can be used to read/write it. Using Python / JS / yq to generate and patch YAML on-the-fly is quite nifty as part of a pipeline.
My main pain point is, and always has been, helm templating. It's not aware of YAML or k8s schemas and puts the onus of managing whitespace and syntax onto the chart developer. It's pure insanity.
At one point I used a local Ansible playbook for some templating. It was great: it could load resource template YAMLs into a dict, read separately defined resource configs, and then set deeply nested keys in said templates and spit them out as valid YAML. No helm `indent` required.
It's the "make break glass situation little easier" option, not the main mechanism.
Use a programming language, a dedicated DSL, hell a custom process involving CI/CD that generates json manifests. A bit of time with jsonnet gets you a template that people who never wrote jsonnet (and barely ever touched k8s manifests) can use to setup new applications or modify existing ones in moments.
My main pain point is, and always has been, helm templating. It's not aware of YAML or k8s schemas and puts the onus of managing whitespace and syntax onto the chart developer. It's pure insanity.
At one point I used a local Ansible playbook for some templating. It was great: it could load resource template YAMLs into a dict, read separately defined resource configs, and then set deeply nested keys in said templates and spit them out as valid YAML. No helm `indent` required.