There is indeed a philosophical part to it around the "do one thing and do it well", but what you call "fear" is not an totally unfounded concern, in that it's true that the more complex a piece of software is, the more complex maintenance also is.

But you need serious technical knowledge to fully understand everything that systemd does compared to sysvinit, what are the advantages of this new system and how much its complexity can actually affect maintenance (or not).

I don't have that kind of knowledge, you could explain to me all the technical advantages systemd has but I wouldn't be able to understand them, so I just trust distro maintainers in doing what they believe it's best for their distro and I never considered the init system as a parameter to choose what distro I want to use, I just use what's in the distro.

Now it's different, because adding a field to comply with a moronic law pushed by Meta to avoid fines has truly nothing to do with technical reasoning, you don't need any tech knowledge to understand that, anyone can.