So it seems like their TL:DR is:
1) Either go with a prebuilt solution like Citus, or be prepared to build an external service locator that allows a human to define the leader so that a human admin can manually trigger the failover;
2) Don't forget that it's a DB and it needs fast storage;
3) Nothing is new under the sun and you need to beware leaky abstractions.
This doesn't seem to me like a reason not to run PG on K8s?