Drop in files (config in .d folders) are a core extension point of systemd and not a symptom of an overly engineered config system. These are how services are m

Drop in files (config in .d folders) are a core extension point of systemd and not a symptom of an overly engineered config system. These are how services are meant to be custom tailored to specific machines and even user's needs. Let's say you need to pass a special flag to sshd on your system, a bad approach would be to go edit the distro shipped sshd.service file. Your change will work until the distro ships an updated file and you forget to hack in your change again. Instead place a sshd.service drop-in config file in the appropriate place to customize the service as necessary. Your config tweak takes precedence over the distro shipped config, but doesn't live inside it or conflict with upstream changes.