Does it really matter if you can’t use those independent binaries with any other init system? If you want to use systemd, you pretty much have to take the whole ecosystem.

If I remember correctly, there was a ton of pain configuring a minimal systemd. I am unaware if that has changed much in recent years.

Here is an old thread talking about it: https://unix.stackexchange.com/questions/150975/what-is-needed-for-a-minimal-systemd-boot-to-launch-getty-on-a-virtual-console