I recall part of the problem was that in some cases, Debian packagers/developers did not know how to integrate systemd with sysvinit properly, there were weird

I recall part of the problem was that in some cases, Debian packagers/developers did not know how to integrate systemd with sysvinit properly, there were weird problematic constructions such as sysvinit scripts calling systemctl or vice versa and some breakage due to the way they used systemd. Of course, one could ask whether this was partly due to bad systemd documentation and unfulfilled expectations of promised systemd behavior.