"Setting up a systemd unit file (it's not even a script) doesn't even come close to the complexity of wrapping, maintaining, and potentially orchestrating software within containers."

I find that the complexity of managing containers is overstated. It does have costs, but the benefits of docker and containerization in general outweigh those costs. Kubernetes is significantly more complicated and is not always a good choice depending on the use case.

"like systemd?"

I find that systemd tries to do far too much for our needs, namely for just managing services in a container. Our images have their services manged by s6-overlay [0], but there are multiple init systems one can use. I do not see the benefit of systemd over i.e. s6 or runit, but that is tangential to this discussion.

[0]: https://github.com/just-containers/s6-overlay