Runit is 5474 SLOCs. Most source files are shorter than 100 lines. Works like a charm. Implements an init system; does not replace DNS, syslog, inetd, or anything else.

Systemd, by construction, is a set of Unix-replacing daemons. An ideal embedded system setup is kernel, systemd, and the containers it runs (even without podman). This makes sense, especially given the Red Hat's line of business, but it has little relation to the Unix design, or to learning how to do things from scratch.