Isn't systemd still optional in Debian? I know there is worry that since it's the default, packages won't necessarily be well-tested without it, but afaik you can still remove it, just by installing sysvinit: http://without-systemd.org/wiki/index.php/Debian_Stretch
it is "optional". unless you run a headless server or a barebones desktop system with very carefully selected packages it is impossible to not install systemd because logind & pam dependencies are littered everywhere. Using sysvinit as pid 1 is achieved by installing systemd-shim, which still depends on systemd and uses systemd files and systemd is still run anyway, just not as pid1. so yeah, there is practically no…
Edits: I should review before posting.