I can't decide between yaml and json5/json

It seems like we will be forced to use both forever though

It's crazy complicated and full of uneccessary cruft. Hence stuff like strictyaml

I wouldn't say it's the most readable. Values can be ambiguous, YAML anchors are powerful but complicated, and using indentation to define structure means that you're never quite sure to which node something belongs to. And good luck hunting down weird errors if you mistakenly screw up the indentation.

YAML is also often abused as a DSL and for very large documents (Ansible, k8s, GH Actions, etc.), which makes it a pain to work with.

It's not so much that liking all of this is controversial. It's just a bad opinion. :p

YAML is as good as we will get.