It breaks the Unix philosophy of doing one thing and doing it well.
Systemd is doing more and more things and that is not good, it has reached a point where it is as or more important than the Linux kernel.
Discussion
Exactly.
Another concern is that systemd is a huge control vector over the Linux ecosystem for the big tech industrial complex:
It's basically a bunch of RedHat (which is owned by IBM) and Microsoft employees who get to design all the standards and steer the course of development.
This "gang" has a long history of pushing controversial changes without consensus from the broader open source community.
Here's an interesting article that goes a bit more in depth about this:
https://unixdigest.com/articles/the-real-motivation-behind-systemd.html
The first blue box in this article from the same blog links to the full announcement of the Devuan fork on the Debian mailing list:
https://unixdigest.com/articles/my-choice-of-operating-system.html
I have read up on all of this a couple of months ago and it really kinda reminds me of the blocksize war and COINTELPRO...