> On StackOverflow: copy/pasting docker CLI (even given proper context fitting into a larger whole) commands and configs probably has a 50% success rate for commands, and maybe 10% if it's a config of some sort (e.g. compose files)

This is not particularly surprising. Docker does two things. One is a filesystem package manager, the other is providing a common interface around dozens of low-level features. The filesystem packaging stuff works well enough. It's the other part that is inherently complex because it does so many things at once (networking, mounts, resource management, security, process management, ...). When something doesn't work you'll end up with old-school linux sysadmin work except that you now don't deal with a single network interface and a handful of iptables rules but dozens scattered across namespaces and complex mount trees.

There's no magic, just convenience as long as you stay on the happy path.