Well, Devuan people made it work, while also maintaining an entire distro fork. This could easily have been made to work on Debian. The alternative would have been to lean on GNOME, I think.
> every single theoretically possible option at install time
systemd-or-not is not "every single theoretically possible option". It is a highly contentious and political issue. If the systemd proponents would have accepted defaulting to no-systemd, then great, no need for the choice; but realistically, both sides are somewhat adamant, so making the user choose is a reasonable compromise IMHO.