Every DBMS comes with its own set of special problems. Most people only find out about the truly tricky ones once they have deployed a database in production (i.e. when it is too late to decide your needs are actually not served all that well by what you chose).

Once a DBMS like MongoDB gets popular, then people uncover some of its failings and write about them...which is great because it means you don't have to discover the same things the hard way. But it's a drag too because there's no database system that everyone agrees is adequate (much less ideal) for every application.

Other NoSQL solutions were not marketed as a replacement for relational databases. MongoDB might be better now,but you cant take managers for idiots an expect them to buy into your product again. Right now MongoDB only lives because of javascript and nodejs ,since nodejs sucks big time with anything that is not MongoDB,library and driver wise.