The article says it was the last one in service/last to be decommissioned in the USN which I think is accurate.
Unless you're counting LHDs
I second that and to avoid any doubt from the horse's mouth as it were, (guess no one can claim that the USN isn't authoritative )
Kitty Hawk had been the Navy's oldest active warship since 1998 and turns over the title to the nuclear-powered aircraft carrier USS Enterprise (CVN 65). Kitty Hawk was also the Navy's last remaining diesel-fueled aircraft carrier.