People want to understand their software as well as it's practically possible. It's not an uncommon preference; worse-is-better was quite successful for a reason. As systemd stands, it's an unauditable mess of tightly-coupled components built to handle any conceivable need. These features create new attack vectors: for instance, systemd-machined credential passing system, which can inject arbitrary files such as keys and configs into the guest, also runs on bare metal. And some are just running a musl system that can't even use systemd.
Some might look at the old SysV init scripts through rose-tinted glasses, but I don't think it represents the current state of the community. We have the modern OpenRC with parallel startup, dependency-based initialization, supervision, network management, and cgroups; dinit, which tries to imitate the 80% of systemd features that people use with 20% of its footprint; s6 with its supervision trees; runit that just works; and GNU Shepherd, which gives you an entire Scheme interpreter to configure your system.
Monocultures are bad because they eliminate competitive pressure for good design and create single points of failure that affect everyone. systemd was an excellent addition to the ecosystem in its day, but has become uncomfortably sticky: you can't just choose to replace systemd; you'll need to reimplement udevd, logind, D-Bus activation interfaces, and now userdb, all of which have their own subtle quirks you'll need to replicate. Look to the state of mdev or elogind and you'll see why it's not a sustainable compromise.