Some people just don't like it. That's their decision. In most cases its emotional.
Beyond complaints about journals being binary, which I get, there's usually not much more to the systemd hatred than "I just don't like it, humph (frown, arms crossed)".
It's an open source world..... the haters have the chance to come up with something that's better and if it is actually better then in the Linux merit driven ecosystem, then the better thing should win and be adopted, right?
Personally I love systemd - unbelievably useful and powerful.
Stallman used to say Linux should be called gnu/Linux because there's some gnu code in many distros.
More realistically it should be called Linux/systemd because systemd defines so much of how the operating system works.