I’d like to chime in in defence of OnyX.
As
@Wowfunhappy noted, OnyX does two things very well: it lets one tweak user interface settings, such as with Finder, Dock, and iTunes, along with other Apple-bundled applications. It also does double-duty as Disk Utility without having to open Disk Utility, letting one run a Verify Disk, repair permissions, as well as rotate logs manually, and rebuild services like the Spotlight index. In a lot of ways, it contains some of the most used features of a utility like Cocktail, but does it all for free and, like Cocktail, has unique versions for each major version of OS X/macOS.
I’ve used OnyX across multiple OSes for several years and I have not run across any OnyX feature which might corrupt a daemon (such as xpcd).