Postgres: A great database but HA options either have far too many moving parts, require manual intervention, are proprietary, or are Fake Open Source. Seems like there's lack of interest in addressing this because companies that sponsor development generate a lot of value off complex operations
MySQL: This database has some odd behavior but that would be fine if it weren't Fake Open Source
MariaDB: HA Options are poor or abandoned
SQL Server: Proprietary
Oracle: haha
CockroachDB: Fake Open Source
YugabyteDB: Fake Open Source. Special shout out here for not even linking to instructions for how to build the database in the readme.
MongoDB: Proprietary, and even before the license change it was Fake Open Source
Cassandra: Not fun to run, and even though I said I didn't care about API I don't necessarily love how it works. But it comes probably the closest?
ScyllaDB: Fake Open Source
TiDB: Fake Open Source
Singlestore: Fake Open Source
FoundationDB: This one comes close but its beginning as a proprietary database really hurt its community, which is way smaller now than it should be. Could grow into something great if more folks got behind it.
etcd: not suitable for use above a couple GB of data
What do I mean by Fake Open Source? A project that has a large percentage of its contributors beholden to a single organization/entity to me is not really open source in spirit. I'm looking for a project where I can feel confident my contributions won't effectively end up behind some proprietary license down the line if/when the VC backed organization that primarily sponsors development decides it needs to protect itself from AWS. If there's an "Enterprise" product and the organization calls the source code for the main project the "Community Edition" or something like it, it's not Real Open Source. If a single organization shuts down and contributions fall off a cliff (https://github.com/rethinkdb/rethinkdb/graphs/contributors) it's not Real Open Source. There are lots of Real Open Source projects with great communities of users/contributors, but many of the newer databases don't have legitimate open source development communities behind them, in my opinion.
I've probably missed some examples. Mostly, I wonder why there hasn't been a general purpose open source database that does the operations stuff as well as the proprietary databases do. Am I missing something?