Well some distros might force more components upon you but thas hardly systemd's fault. Same if some software decides to make use of another component of systemd - then that's their choice, but also there are alternatives. The only thing that comes to mind right now would be something like GNOME which requires logind, but all other "typical" software only wants systemd-the-init-system if anything. You can run Debian just fine with just systemd as an init system and nothing else.