systemd managed to replace init, inetd, and some of cron in what appears to be a stable environment. This allowed systemd to work in docker and drastically improve Linux virtualization to leapfrog Solaris zones.
What systemd did not do was provide reasonable documentation. RedHat's v7 inittab has a website for a blog post that sucks. There is no general intro for users attempting to create crontabs executed by systemd, inetd entries for common services, and runlevels that control groups of processes.
systemd fell down hard on documentation, and the first blush with the unix admin crowd has not been kind.
These developers delivered working code in a radically new environment, but without documentation the architecture appears to discriminate against people who have been doing things the same way for 30 years. The authors, and their software, appeared cliquish and discriminatory. Had the software and the documentation enabled a gradual migration into a more powerful architecture, things would have been quite different.
In any case, this is no justification for people to be vile. The old crowd needs help into the new environment. This help needs to happen, and the insults and threats need to stop. Both sides need to work together to get us where we need to be.