There aren't decent Pro systemd arguments other than "the Linux API confused me" and sysv init (which no one argues is good) was bad.
Personally the last system I had systemd on corrupted my package database after killing apt that I was running in tmux. "Oh you can fix that with xyz systemd configuration." Here's my response:
Kindly shove it up your ass and quit moving things around all the time just because you're board.
Also if "it's good enough for most people" is a decent argument then you should be on Windows.
The pro argument is that writing shell scripts for starting/restarting/enabling/disabling/stopping is total garbage. Not to mention having to manage lock files. systemd units are not perfect, but they are a billion times better than the crap we used to deal with.
The pro part is the massive simplification and security advantages systemd brings to plain and simple config files. Sure, I can reimplement the containerisation API in OpenRC if I stack enough helper binaries and shell script libraries in there, but I don't want to. Kindly shove it up your ass and quit moving things around all the time just because you're board.
If it's good enough for most people, that means it's good enough to use as a basis for development. The same way no company develops mobile apps for Phosh or Plasma Mobile: the tiny fraction of people who have more esoteric preferences aren't worth rewriting the software stack for. Those who don't like the status quo can write their own wrappers and hacks if they want to use your software.
It is weird to name something as a "massive simplification" when saying that it is intended to replace "plain and simple config files". "Massive simplification" is a term that may be applied to something like the daemontools of Bernstein and to other systems inspired by it, but certainly not to anything based on systemd, where it is much harder to discover what it really does, when problems appear.
Perhaps systemd has "security advantages" over alternative solutions, but I have never heard of them and I cannot imagine them, so please name them.
So your software broke my machine then you tell me it's my problem and wonder why people are angry and frustrated with you?
Do you see why most competent people's reaction is to just use something else? systemd might even be technically superior but the maintainers are such assholes it's not worth it.
Personally the last system I had systemd on corrupted my package database after killing apt that I was running in tmux. "Oh you can fix that with xyz systemd configuration." Here's my response:
Kindly shove it up your ass and quit moving things around all the time just because you're board.
Also if "it's good enough for most people" is a decent argument then you should be on Windows.