It’s prolonged downtime, that’s what it is, and it may make the system unusable. I saw that several times during the transition period where a network outage or data center shutdown meant that some important daemons failed on startup (one of them had the concept of retrying a connection error, but not a DNS resolution failure) and the admins of the SysV boxes had to manually restart everything while the Upstart & systemd boxes recovered almost immediately. One fun case had the developer almost getting this right: they had implemented retries but without a time delay or back off so their init script maxed out its retry count in a second of “host not found” errors and then exited permanently.

When you leave things like retries, logging, or dropping permissions up to each daemon you end up with a hodgepodge of incomplete implementations and things like error handling are where corners tend to get cut the most since the situations are infrequent and often hard to simulate.

Really, it's only on you to fix it if it does not work, which in my experience is far less likely with systemd.