You're right, NoSQL systems tend to be more complex and especially failure scenarios are hard to comprehend. In most cases, however, this is due to being a distributed datastore where tradeoffs, administration and failure scenarios are simply much more complex. I think some NoSQL systems do an outstanding job to hide nasty details from their users.

If you compare using a distributed database to building sharding yourself for say your MySQL backed architecture, NoSQL will most certainly be the better choice.

I'll admit though dealing with NoSQL when you come from a SQL background isn't easy. Even finding the database that fit your needs is tough. We have blog post dedicated to this challenge: https://medium.baqend.com/nosql-databases-a-survey-and-decis...