This functionality is (mostly) obsoleted by the newer
GLIB_VERSION_MIN_REQUIRED and GLIB_VERSION_MAX_ALLOWED defines. With
this, your build doesn't all of a sudden blow up if we deprecate
something in GLib - you have to explicitly opt-in to the newer
version.
G_DISABLE_DEPRECATED does still apply for macros and things that can't
take __attribute__((deprecated)), but it's not really worth the pain
and cargo culting around just for that.
nmcli uses its own code to dump connections' details instead of
libnm-util's nm_connection_dump(). It allows to structure output
and present values of the settings according to nmcli needs.