How many systems actually need a distributed database though? In my experience its usually resume driven development that makes the choice to go NoSQL.
Dear God, this. 90% of the people reading this (or more) - myself included - are currently working on a system that averages fewer than 100 concurrent users. I’ve worked on big systems, and DBs like Cassandra are great, and absolutely have their place, and that place is likely not your system. Quit over complicating everything, please. Please.