Yes, that list reminds me of the exaggerated posts about "look how hard it is to install Firefox on Linux!!". Claiming that setting up a Debian Postgres server necessarily entails knowing ZFS and Kubernetes is quite a reach
Not sure about Debian, but I believe Ubuntu Server will let you setup an mdadm mirror, LUKS (with LVM), and install and enable a Postgres server with a few buttons in the install wizard. It can even fetch SSH authorized keys from a Github account, covering by far the most important SSH hardening step (disabling passwords). Most hosting providers will also offer a one-click deploy that may similarly add your keys and do other common config
A better example of something that hosted databases makes a lot easier out of the box would be backup, replication, and monitoring
I'm not sure. I rather use a lightweight kubernetes or perhaps nomad than do everything that kubernetes does without it. It sounds even more complicated. But I agree that for one single postgresql isolated from everything, kubernetes is overkill.