> However, most self-hosted software is already "pre-packaged" in Docker containers. It's much easier to grab that "off-the-shelf" than have to build out something custom.

Imo, the quality and documentation level of an application's build system is a valuable signal in determining its overall health and competency. It usually (though not always) ends up being that well-maintained software written for modern runtimes is very easy to build from source and run. Even if I do end up using the developer's container image, I generally want to check out their manual deployment documentation.