Systemd does a lot of things right: Having one process for the init, declarative definition of common options, streamlined interface. Note that many distros used to provide shell libraries for the same effect, but ended up with incompatible init scripts.
In the end, the init script style is just the bare minimum that works solely by POSIX features and is a PITA when it comes to advanced use cases like dependencies or machine-readable system state or platform independent init definitions. Systemd is certainly not the ultimate tool ever written, but it is a bold step in the right direction. Maybe someone will rewrite it someday (if so, presumably in rust) and I will appreciate the effort to make things even better.
In the end, the init script style is just the bare minimum that works solely by POSIX features and is a PITA when it comes to advanced use cases like dependencies or machine-readable system state or platform independent init definitions. Systemd is certainly not the ultimate tool ever written, but it is a bold step in the right direction. Maybe someone will rewrite it someday (if so, presumably in rust) and I will appreciate the effort to make things even better.