Kubernetes or Swarm are not enough, you also need storage replication. At work we’re using Portworx but it’s a commercial solution, not suited for normal SNOs.
GlusterFS is slow and buggy, if you want to be disqualified, that’s the right solution.
Anyway, I generally agree with you, but how many SNOs are able to setup a HA solution using one of the techniques you pointed out?
There are many products that use native replication rather than relying on the underlying raw storage replication: etcd, Minio, Kafka, ActiveMQ, almost all databases like MongoDB, Postgres, etc. and many other platforms all use internal replication. Did they all reinvent the wheel?