This is the over the top hyperbole the OP was talking about. Even if systemd did "replace Unix", I don't know why anybody should care.
As a long time Linux user it's clear that Systemd took over because it's better. The old way of doing things was a complicated mess that had evolved over decades, and was difficult to use and understand, with lots of weird interactions and no consistency.
Having a standard way to do admin tasks across all of the distros is valuable and makes Linux easier to use and more reliable.