MongoDB has come a long way. They acquired a world-class storage engine (WiredTiger) and then they hired some world-class distsys people (e.g. Murat Demirbas). They might still be hamstrung by early design and API choices but from what I can tell (never used it in anger) the implementation is pretty solid.

MongoDB is a very good database, and these days at scale I am significantly more confident in its correctness guarantees than any of the half-baked Postgres horizontal scaling solutions. I have run both databases at seven figure a month spend scale, and I would not choose off-the-shelf Postgres for this task again.

mongodb is a public company with a market cap of 14.2 billion dollars. so yes, people still use it in production

I've been looking for a job the last few weeks.

Literally the only job ad I've seen talking about MongoDB was a job ad for MongoDB itself.