Earlier quoted context omitted.
Why? Sincere question - AFAIK, Raspberry PI OS is a Linux distribution like any other, with dependency/distribution issues like any other. Why would using Docker on it be a sad state of affairs, in contrast to using it on any other distribution?
Because a password manager is a tiny piece of software. Instead, it is now a multi-component black box installation with a general purpose operating system running on a full-scale Linux machine with a containerization platform designed for datacenters. I am not a fan of this kind of redundancy and opaqueness.
There seem to be some other Docker features used, like healthcheck [0], and MariaDB seems to be installed, too, so it might be worth considering how much additional OS-dependent complexity would the equivalent functionality without using Docker require. At the very least, you need some kind of service manager to run your program on boot, and restart it on error. At that point, Docker may as well be used as a glorified service manager - just slap your static binary in a `FROM scratch` container, and you're done.
> I am not a fan of this kind of redundancy and opaqueness.
Me neither. But I wouldn't blame Docker itself - it's just a tool. If it wasn't for Docker, some other way of circumventing good engineering would be found :-)
[0] https://github.com/dani-garcia/vaultwarden/blob/main/docker/...