I came across a thread and an article1 about systemd, which made me feel grateful that Slackware is unaffected by this apparent madness. The article gives a nice point by point overview (it may be a bit biased, it's called ‘boycott systemd’).
I read that Gnome depends on it. I've actually never used Gnome, ever. I remember using KDE 1.0 in the beginning, dropping KDE when it got to version 2.0 (which I hated) for Fluxbox, dropped that for Openbox after about a year and have been using Openbox ever since. Whenever I took a peek into KDE, I fled. This idea of a ‘desktop environment’ doesn't appeal to me at all. Just use the programs you like, no need for all the other stuff using up resources.