Even if OP is using 5.6 or previous, strict mode has been available as an option for over 15 years, and can be enabled dynamically (no restart required).
I simply don't see any valid argument for avoiding MySQL due to "data reliability" concerns in 2019.
> There were other minor deficiencies mentioned in Klepmann's book on Designing Data apps, but I don't remember the specifics now.
Well, I can't really respond to non-specific points from a book I haven't read. I'm happy to respond to any specifics re: data reliability concerns, if you want to cite them. FWIW, I have quite extensive expertise on the subject of massive-scale MySQL (16 years of MySQL use; led development of Facebook's internal DBaaS; rebuilt most of Tumblr's backend during its hockey-stick growth period).
It takes years to build up trust, seconds to lose it. Obsolete documentation to disappear. It's an uphill battle. In the meantime there's postgres, and it's free.
There were other deficiencies mentioned in Klepmann's book on Designing Data apps, but I don't remember the specifics now.