I think the point of the article is that Mongo is being used mostly by "poor carpenters", and provides worse defaults than SQL does. It's obvious you're operating at an advanced level that young and hungry startups aren't.
It's the difference between assembly language and a high-level language. Key-value stores are simple, basic, and primitive. What's wrong with that? It's like a farmer saying, I don't want to learn how to use a tractor (it's too complicated), and who chooses to farm with a hand tools instead.
> if you use tools you don't understand
Yea.... key-value stores are incredibly complex and require years of learning to understand.
I could explain a key-value store to a five-year old. In fact, I think even a pigeon can understand the fundamental principle underlying a key-value store. https://en.wikipedia.org/wiki/Pigeon_intelligence
For any non-trivial data model, go with something that can capture your model at a high level, like a relational database or a graph database.