Being boring has nothing to do with scale. Some of the biggest applications run on incredibly simple architectures, and often are able to scale so well because of that (boring) simplicity.
There is ScyllaDB for a much better reimplementation of Cassandra/Dynamo, but wide-column databases are still best for niche scenarios, especially as RDBMS are rapidly evolving into natively distributed architectures.
Everything from StackOverflow to ad serving systems to high-frequency trading exchanges are run this way.
Quora, Pinterest, Twitter, etc are all just big app instances talking to DB instances, with separate systems for background processing, queues, and caching. Are you suggesting that they would scale better with serverless functions instead?
Here's a list of architectures: http://highscalability.com/all-time-favorites/