The thing is most applications don't really have data across regions that are related. So, there really is no need for distributed databases for most of the use

The thing is most applications don't really have data across regions that are related. So, there really is no need for distributed databases for most of the use cases which actually can be solved by sharding. Also, most of the applications already gracefully handle DB failures by failing over to stand-by replicas which PgSQL and MariaDB already provide. However, I do think the key innovations are in building control planes around existing relational and NoSQL databses for scaling/sharding them across a set of resources to minimize cost while meeting performance and availability constraints.