systemd-resolvd is, like many of the systemd components, optional. If you're using it, it is either because you setup it yourself or your distro set up it to y

systemd-resolvd is, like many of the systemd components, optional. If you're using it, it is either because you setup it yourself or your distro set up it to you or you're using a NetworkManager with systemd-resolvd as your DNS resolver (and even them, it is configurable and not the default at all).