Not really. Systemd could have fixed it, but it would have been a lot of work and a hack. The Linux kernel team could have fixed it, but it would have been a lot of work and a hack. The hardware manufacturers should have fixed it, but they don't care.
The Kernel team showed they are professionals by stepping up and doing the work.
What you mean is: systemd could have fixed it, but it would have been a lot of work and a hack that wouldn't help you when efivarfs gets mounted on a sysv/upstart/openrc system. The kernel was the best place for the fix.
disagree. It's not just systemd that could mount efivars as read/write, anyone could. So anyone that does will fall prey to this. It's firmware, and failing that, the kernel protecting you is a good second.
systemd couldn't have fixed it, because removing the offending code from systemd wouldn't have prevented any other program from, innocently or maliciously, triggering the same bug.
The kernel is where the buck stops when it comes to protecting hardware and, therefore, protecting software from misdesigned and/or buggy hardware. That's been true for longer than most of us have been alive.