My general feeling is that MongoDb was designed by people who hadn't designed a database before, and marketed to people who didn't know how to use one.

Its marketing was pretty silly about all the various things it would do, when it didn't even have a reliable storage engine.

Its defaults at launch would consider a write stored when it was buffered for send on the client, which is nuts. There's lots of ways to solve the problems that people use MongoDB for, without all of the issues it brings.