> Choosing a system that only offers very few guarantees forces you to think about them more explicitly.

Yes, of course. And it also forces you to implement, on your own: relational (key) constraints, real transactions, etc.

And thus, you, on your own, compete against more or less 44 years of research, developing, and releases by brilliant computer scientists and engineers (Ingres DB, 1973- PostgreSQL latest version, 2017), scientists who already solved those problems {relational constraints, transactions, etc} and made said solutions perform to the max possible.

So a better alternative is to simply... learn more about relational databases.