On this #FreeBSD laptop, I just use startx to run #openbox. I've done that on plenty of #Debian systems in the past....even in its lighter days with #sysvinit. It it helpful with multiple users, however.
As for #systemD, if it were just an init manager I'd have less of a problem with it. Creating "unit files" and where things are located are convoluted at best.
SystemD has its tentacles in other traditionally non-init things like /etc/resolv.conf and others. That's where my biggest problem lies.