Systemd is pretty nice when it works and there are certainly a lot of things it does well that i find convenient.
1. A lot of the "benefits" systemd has are not systemd-specific — most other modern init systems do have them as well (parallel startup, easy service creation…) (see OpenRC, runit…).
Systemd devs and zealots mostly only ever compare it to the old sysvinit scripts which are awful and SHOULD be replaced by something more modern.
2. Systemd is huge — and it's only getting bigger.
Systemd now includes a lot of other things which it doesn't need to, like udev, which are crucial to modern Linux distros and thus creates a dependency and restricts user's choice. While systemd's proponents claim it's modular, it is modular in the sense that it's not one huge binary, but it's still a lot of tightly-coupled components which are often not easily replacable by a non-systemd implementation. Coupled with the fact there is no stable API (as the API used between components is only internal, not documented properly and ever changing) it is next to impossible to make a replacement for the "independent" systemd modules.
3. Systemd devs are known to be egoistic assholes.
I'm trying to be as unbiased as possible in this answer, having used systemd myself for years and liking a lot of its features. But they've clashed with Linus, expecting him to change the kernel because they used a feature for something it wasn't intended and wanted to keep doing that, instead of fixing their code. There are multiple instances of them giving a "not a bug, but a feature" response to various critical bugs, like your (binary) journal getting corrupted and completly unreadable under certain circumstances. "Yes we know, but that's just how things are." That's not what you want from people developing such crucial part of your os as is the init (and various other pieces systemd's devoured in the meantime).
AFAIK systemd still soykafs itself trying to shutdown with a network mount because it brings down the network before trying to unmount it, leading to a 90s delay.
Should give you an idea that not everything is as rosy as they claim.
Personally, runit gives me all the convenience of systemd with none of the problems and I'm very satisfied so far. But it has only been 2 months so that might change in the future.