We've used a some of Distributed storage (Longhorn, OpenEBS) things for Kubernetes and had no luck.

I agree with you at ALL the things you've listed. When we've started to used Ceph for the first time - (At that time I was an user, not a Manager) all the thing was a total mess. All the things are set to default and Use all JBODs on Node. (And I've started to face Corrupted WALs and OSDs came from nowhere.)

The handful of documentations was very helpful to cleans up and make it to run correctly.

Maybe, when I go back to the starting point, I'd like to say "move to cloud" or "do nothing" or following your guidance.