> it becomes a pain once you start trying to use it like a DSL or templating language.
I like YAML and use it a lot. But I'd argue the fact that it even allows/encourages you to do such things with it is a design flaw that ultimately has kept it from Do One Thing Well.
I do think some of the more "advanced" features are definitely a mistake. StrictYAML (https://github.com/crdoconnor/strictyaml) is a limited, much saner subset of YAML that I wish people would use more: https://hitchdev.com/strictyaml/features-removed/
No coercion of y/n/yes/no/on/off to booleans (these were also removed in the official YAML 1.2 spec, thankfully), no direct object representations, no anchors or references, etc.