they wernt Kages till recently.

Their official titles were jounin, Orochimaru is only a kage to the sound village, hes not an official kage.
Tsunade is only recently a kage and Jiraiya is still a jounin

Kage is a title you can get the moment you own a village, its not an indication of skill level, their actual titles are jounins


Zabuza was still a jounin even if he was a missing nin by the way