Per the Wikipedia entry (https://en.wikipedia.org/wiki/Systemd#Adoption), Debian, Gentoo, Slackware, Knoppix, Mint, and others will all run without it (ie you have a choice in your services management system, or systemd's not included at all)
What do you not like about systemd (if anything)?
Overall, I think the systemd way of managing boot sequence and services is at least equivalent to (if not superior than) the old init system (which was all I knew from the Red Hat world) or the BSD-style boot scripts (that Slackware uses)
There are other service/boot managers out there (https://en.wikipedia.org/wiki/Init mentions launchd and runit among others)