Because systemd confuses a lot of things by having two projects with the same name.

Systemd the init service is excellent.

Systemd the catch all for trying to rewrite all services to come up with a baseline version of everything is a strange and NIH project. They would have been far better off politically by coming up with a spec and seeing if they could submit patches to get the current services to use the APIs they were planning.

Instead they just have a bundle of things they have tried to reinvent, some more successfully than others. Hence the divisions in the communities.

Okay so back in ~2000 the audio system in Linux was ALSA and it kinda sucked so along come a guy named Lennart Poettering who wrote pulseaudio which improved things in a lot of ways but also kinda constantly didn't work. Poettering in those years constantly blamed everything on other software in the stack and became kinda wildly disliked. We all had to use pulseaudio though because everything important decided to integrate it.

Jump forward to systemd and absolutely none of trust Poettering farther than we can throw him. At the same time systemd basically did the job of half a dozen programs which offends a lot of people on philosophical grounds. Simultaneously a bunch of things start hard requiring this program that people neither trust nor like.

It is a fantastic init system/service supervisor. My problem with it is basically everything else. I think its developers see systemd as central to the entire system, basically the userspace counterpart to the kernel. I prefer the approach of 'dinit', but I understand why they designed it that way.

Due to this design they often have underspecified interaction between the different components, since the assumption is that everyone will use largely the same baseline systemd environment and as long as it works, who cares what it does underneath. If the different parts were more independent, they would be forced to develop a cleaner API contract between them.

It violates the Unix philosophy of 'do only one thing and do it well', but personally, it has never been a problem for me.

I had a nightmare last week wherein I read a headline that systemd was writing its own kernel. When I woke up I realized it was a possibility, after all it has replaced GRUB. https://wiki.archlinux.org/title/Systemd-boot

People seem to think it tries and do too much. As a sysadmin I love systemd, especially way more than the init scripts it replaced

The way it's structured (combining many previously separate utilities into one) hinders competition. That's tolerable while it's still one of the best solutions for the things it does, but will become an issue in the future.

I wasn't there but from what I understood was that people didn't like the fact it was re-inventing an already-existing wheel. In the long run it was useful for some (at least for me it was).

I unironically believe Docker is a great deal of a reason why it has freshly opinionated newcomers.