I didn't mean single binary either.

I meant, that systemd solves some category of problems, that other tools didn't solve, didn't intend to solve and didn't even care for what the problems are. For distribution maintainers, systemd was something to welcome, that did address their problems.

So yes, there is no replacement (the requirement for it being drop-in only places the bar higher), because there's nothing else that scratches the same itch.