On a desktop, systemd and firewalld make sense, because one might have an Ethernet connection that is in a trusted zone, a Wi-Fi adapter that is on a public (untrusted) zone, and so on. Plus, the parallel startup of systemd makes booting a lot faster.
For a server, one wants reliability and security above all. One reason why IBM still obtains boku bucks is because AIX 7.1 still runs applications written for 3.2.5. It might require some compatibility programs to be installed, but if one wanted to run FrameMaker or WordPerfect under Motif, they still can, assuming a graphics card present.
Server-side, it doesn't matter if things start in series. Things need to work properly and be coded for maximum security and reliability.
systemd is the iTunes of the Linux world. It does so much in userland, that a bug in that can mean disaster, or a series of disasters similar to the tons of sendmail holes found in the early to mid 1990s. While it does improve some things, having a large, monolithic package handle so much of userland can mean big trouble .
My personal take: systemd is a leap forward. But, for something this crucial to infrastructure, with so many moving parts and so many different interactions between them, this really needs to run through a bug stomping session. Maybe Facebook would torture-test it like they are doing btrfs so that virtually all the major bugs get squashed sooner, rather than later. Even better might be a formal code audit on it (a la TrueCrypt) to find and squash anything that could cause the next Shellshock or RTM worm in coming years.
The one thing that has kept the epic fails out of UNIX is the fact that the OS is made out of a lot of little subsystems. Replace bash with busybox, not that many programs would notice. Replace /bin/yes with busybox's yes... who cares. However, systemd breaks this philosophy. If something breaks, I can't just rename the binary, link in the busybox equivalent, and call it done. I'm dead in the water until a patch comes out, and since this is a subsystem that completely controls the userland environment, this is worrisome when it comes to production critical items.
: Ironic how this is similar to what Tanenbaum said about the Linux kernel.