There are a lot of problems in YAML, but I think the main real problem is trying to put logic inside configuration. YAML is still one of the nicest human-readable and -writeable data formats if it is only used for data and not logic.

CI/CD always has some logic, and it's almost never in pure YAML but also has some weird templating going on. Like, please, couldn't you just have a real API for some real programming language.

That's not really a problem with YAML it's an abuse of YAML. Accidental turing completeness is a problem all over, too. I remember using Ant 15 years ago - built in XML. It was the same problem and that wasn't XML's

I think a lack of type safety is the main problem with YAML - a wrong indentation, a typo in a key, a string that gets parsed as a boolean, etc.

Other than that I think it's a great format - terse and far less syntactic noise than other formats. This is why I wrote https://github.com/crdoconnor/strictyaml so people could write type safe yaml and get instantaneous, clear error messages on those things.