Some of the configuration is plain text: unit, service, and environment files are plaintext. Which services are enabled and disabled cannot be controlled through file manipulation that I know of. Journal (log files) are binary.

I think what bothers me about both is that the presence of text files in a predefined location is not enough to make things happen on its own. Instead of the simplest possible everything-is-a-file and interacting with the filesystem is the interface, you have an additional requirement of calling binaries and their subcommands.