It forces you to think of stability instead of creativity, and that might be great for people who value predictable things in their lives, but it stands rigidly in the way of fun.
Technically, I guess it’s interesting to design if you are an expert but as a user, having to use creativity is the last thing I want from low level pieces of my OS. If you want to tinker with OS design, you can always install Minix in a VM.
I don't know about fun, but different people find different things fun.
I find systemd to be often irritating, and sometimes infuriating. It has not made my life easier at all. Just the opposite. So, in that sense anyway, I'd say systemd is much less fun.
Every distro did init scripts in different, exciting ways, so I had to start over from reading the not-inconsequential docs for each one. The init systems come with some high-level helpers, but only if you want to use the shell, which is very unfun in its own right.