OK. So, given those valid arguments against it, which distros don't use systemd right now?

Because it seems that it would be really easy for a new distro to gain users by simply not using systemd, and staying with SysV init or similar.

Slackware, Gentoo/Funtoo, CRUX, PCLinuxOS and all its derivatives. Then some more niche ones like Alpine Linux (which also eschews a lot of the GNU base system for alternatives) and Void Linux.