Why would you say duped? Is there some major problem with mongoDB? The way you've stated this makes it sound like there's some common knowledge I should be aware of.
Yes, plenty. It's mostly useless for relational data.
Nowadays that's clear on the documentation and you won't get loud people proclaiming that it's useful there, but there was a time when both of those were false.
Just keeping invariants of any kind is already non-trivial and will probably break at some point in a long lived system.
Anyway, I was focusing on invariants. But yes, destroying your performance every time you need an atomic change or joining values also makes it bad for relational data.
That doesn't mean it's useless, just that it should not be used on the most common problem people have with their data.
For example: they measured Query B execution time on postgres: 41m3s, mongodb: 1h13m3s. When MongoDB measured Query B with a supported driver, the execution time was only 3m30s more than 10x faster than postgres!
You'll find details here: https://www.mongodb.com/blog/post/benchmarking-do-it-right-o...
Say you have some json and nested in it somewhere is an array of objects, and you want to just map over that and update those objects. I was writing a migration to do that in Postgres <11 once and it was not fun to try and figure out how to do it.
I haven't worked with Mongo in years though, so no clue how it has evolved since like 2015.