a raw YAML file is readable with your eyes. A Json file needs to be prettified before you go thru it. Json is good for APIs but is not made for readibility.

We must disagree with what "readable" means then. I find JSON readable (as long as it's nicely layed out, e.g. by piping through 'jq "."'), in the sense that I can skim over the structure looking for [/]/{/}/". If I want to read some of the content, like a string, I just need to read '\"' as '"' and '\\' as '\', which is a small constant cost per (usually rare) occurrence.

With YAML it's difficult to even know the structure of what I'm looking at, due to anchors and extensions. It's also hard to discern structure from skimming, since strings can appear unquoted, and may contain unescaped lexical tokens (depending on which particular symbols it started with); hence we must carefully consider each and every character, rather than just skimming for the next token.

If I know I'm looking at a perfect YAML file, than I should be able to guess the gist of what it says, since I can make assumptions about what the syntax means. If I want to be sure, I'd be Googling for cheatsheets. Yet as a programmer, I mostly look at files when they're buggy, meaning I can't just assume that, say, an unescaped quotation mark won't terminate the string; or that a certain piece of text is allowed to run across multiple lines; or that the indentation corresponds to the nesting; etc.

That's what syntax highlighting is for.

I use notepad++ for YAML. Besides coloring what it thinks I'm thinking, it displays vertical lines corresponding to the indentation levels.

(I prefer INI/TOML whenever I can help it; hierarchies in TOML are so counterintuitive that it incentivizes a simple flat structure. But then, some things are irremediably hierarchical)

Is it really though? The implicit typecasting gives rise to very unexpected results, that you'd never get with JSON. See: https://hitchdev.com/strictyaml/why/implicit-typing-removed/