> By what metrics can we say the product is one worthy of passing a HN smell test?
Common sense and formal education? I'm sorry, I'm aware of how incredibly snarky and arrogant that sounds, but in this case I always struggled to comprehend how MongoDB, or most of "NoSQL" in general, was considered viable to begin with.
"Schemaless" just immediately means that instead of the database keeping consistency, you now essentially have to do all your type and constraint checking in the application; I never understood how that's favorable, and how that remains maintainable in any way. On top of that, NoSQL (and maybe Mongo in particular?) also decided to throw away all guarantees that classical SQL databases have been offering for multiple decades for very good reason.
I think everyone who's had a somewhat theoretical class on databases and learned about, for example, what ACID really means, will have smelled that something doesn't quite add up here.