Starting with 9.x, you are no longer allowed to log in to privilege mode directly. The prior command was deprecated as you stated. There have been quite a few changes in this area with security being a bit more strictly enforced. You can check out the 9.0.10 security guide for all available options. Let me know if you have any questions/concerns.
Ben Beck, RCNA, RCNI, Principal Technical Support Engineer support.ruckuswireless.com/contact-us