People like to criticise NoSQL databases like MongoDB etc but at least they took on the challenge of making clustering easy enough to use and safe enough to rely on. Especially because it such a complex and error prone challenge.
Cassandra is one of if not the best since it's multi-master but it's a little bit more complex to setup.
MongoDB has definitely come a long way in terms of HA, but yes, they are still have a long way to go. A good primer talk on the differences can be found here: https://www.scylladb.com/tech-talk/mongodb-vs-scylla-product...