That might be true for Unice, but it's far from true for *nix.
In the 37 years since SysV init was released, I think I can count on on both hands the number of times I've had to actually code something that it couldn't handle. All of those cases were extreme edge cases. And note that in none of those cases would the systemd-cancer have been any help. In over half of those cases, BSDinit worked where SysVinit didn't.
That's not to say that a replacement is not overdue, but the systemd-cancer is not that replacement.