I don't remember the exact issue that encouraged to finally abandon MongoDB but I do remember being super frustrated that I wasn't able to find a solution over several days.
I'm using RethinkDB these days (yes, I know it's a zombie database) and I friggin' love it.
Doing the $LORD's work. I haven't contributed much to RethinkDB but it's such a great piece of software. It was doing things right basically from the beginning -- also has great Jepsen reviews[0][1] (if you ever need to defend it -- it's one of the better ones).
The Admin GUI was one of the things that made it an instant click for me -- it's a fantastic tool and I want to run it as a service someday, feels like the only way it can gain marketshare again is if some company pushes it sustainably.
I'm using RethinkDB these days (yes, I know it's a zombie database) and I friggin' love it.