There are many. Most amount to complaints about sysadmins having to re-learn a lot of stuff, much of which didn't actually need to be changed, at least not so thoroughly. Early on, most of the complaints centered around the poor migration path, the abandonment of plain text log files, and the absurdity of high-level user-facing software like the Gnome desktop environment having a hard dependency on a particular init system that many felt was still kinda half-baked. systemd as a project has also been a poster child for feature creep, and while technically many of the new features that have been added over the years are optional, in practice few distributions make it easy to partially opt-out of new systemd stuff. And through all of the controversy, the systemd maintainers have shown a stunning inability to acquire diplomacy skills; systemd has succeeded more in spite of their ability to promote it, rather than because of it.