That's far too reductionist. For a start, there are many sysv-compatible init implementations that do parallel boot; upstart does it, Mandriva's pinit does it. There's a whole subset of LSB that exists exclusively to provide a way for sysv initscripts to represent dependencies *precisely in order to enable parallel init* - see https://wiki.debian.org/LSBIni... for a good write-up of that.
Secondly, insofar as systemd is intended to improve boot speeds, it wasn't actually just about implementing simple parallelization of sysv-style services using dependencies. If you read http://0pointer.de/blog/projec... it talks a lot about parallelization but it's actually talking about making *more* parallelization possible, not just *implementing* parallelization: the big idea Lennart had back then was the idea that you don't actually have to completely start up a service in order to start up another service that 'requires' it, if you can create the socket it listens on before it's ready, then queue up any requests and pass them on to the service once it's actually done starting up. Lennart was clearly really excited about this idea at the time, but if you look at systemd these days, it's a really pretty small corner of all the things it does.
All the way through the first part of that first post, Lennart is really talking about making more parallelization possible, he's not simply talking about implementing inter-service dependencies.
These days systemd does an awful lot more, and it really isn't just about making boot faster any more. Even in the very first post, once you get past the first half, it starts talking about improved capabilities. I find startup speed the least interesting thing about systemd, really, I'm much more interested in the improved capabilities for units and especially in the improved logging journald provides.