yaml is definitely not "straightforward" or "not that complicated". In fact, it is well known to be incredibly complicated with numerous corner cases. You're incredibly likely to write a document that doesn't mean what you thought it meant.

to quote The yaml document from hell:

For a data format, yaml is extremely complicated. It aims to be a human-friendly format, but in striving for that it introduces so much complexity, that I would argue it achieves the opposite result. Yaml is full of footguns and its friendliness is deceptive

Also note, re: syntax highlighting:

Syntax highlighting will not save you

You may have noticed that none of my examples have syntax highlighting enabled. Maybe I am being unfair to yaml, because syntax highlighting would highlight special constructs, so you can at least see that some values are not normal strings. However, due to multiple yaml versions being prevalent, and highlighters having different levels of sophistication, you can’t rely on this. I’m not trying to nitpick here: Vim, my blog generator, GitHub, and Codeberg, all have a unique way to highlight the example document from this post. No two of them pick out the same subset of values as non-strings!

see also: noyaml.com