Have you looked at the list of Linux features that systemd requires? Have you ever read through that list and given serious consideration to how much work it would require to duplicate those features on another platform? I have, and doing even a fraction of it in a remotely acceptable and maintainable way would easily make for a full-time job. Do you happen to know a half-dozen OpenBSD developers with the time and inclination to do this work, continuously? If so, why shouldn't they work on the corresponding Linux-compatible kernel features instead, so that non-systemd programs can use them too?
I think this article highlighted the critical problem: Linux development has accelerated to the point that some other OSes don't have enough sparse developer time to keep up. Yelling "wait up" doesn't change that, it just slows Linux down so that other OSes have a better chance of keeping up with it.
I consider the BSDs a valuable part of the community, and I'd rather have multiple awesome OSes to work with rather than one awesome OS. However, I'd rather have one awesome OS than multiple less awesome OSes.