That's what I was trying to get at -- yes, you can say that sysvinit is easier to understand than systemd, and less of a black box. But, even still, a "real Linux distribution" is full of these black boxes, especially the closer you get to being able to run "real applications". I'd argue that once you get into full desktop seat management, you add so much complexity on top of sysvinit that the difference narrows...

Which is why I asked "learn about what stuff". I think if the goal is to learn about "Unix" or OS design/ideas, you're better off with a leaner, "pedagogical" OS, like xv6. If the goal is to piece together an OS and really understand each piece, I don't think you really want sysvinit. You want something closer to an /etc/rc.local that just kicks off a few daemons and hopes for the best.

You can argue that sysvinit makes a better "compromise" between usability and clarity, and I'd entertain that idea, but then I think dinit is far easier to understand than sysvinit. And of course, at that point you can shave yaks till you fill the bike shed with wool.

Realistically, as much as people may hate it, if you have to pick a single init to standardize on for clarity and "building an entire Linux distro from the ground up, understanding how every piece fits together", systemd is the most rational choice. It's the most representative of the ecosystem, and requires the least "extra layers" to make the "desktop layer" work.