[imoldtoo]

A big problem is MongoDB isn't schemaless, it is document oriented.

That is a really big schema choice imposed on developers and the root cause of for instance why it took years to be able to create good indexes on inner fields, and they still can't do it efficiently.

The same can be said for simple key value stores.

True schemaless databases are much rarer and provide developers orders of magnitude increases in terms of flexibility, expression and speed.

Unfortunately these kinds of databases are not readily available to a broad audience. It's also the case that for the majority of jobs and developers SQL based stores are still a very good choice unless you need to deal with huge amounts of data from disparate sources without bringing down the system.