They absolutely are not a playoff team without Kiffin and it's a joke to think that coaching doesn't matter at all at the highest levels of competition.
It's different when a coach is "suspended" for a game, that means they can't be there, but they still gameplan, run practices and basically set the whole staff up to execute for Saturday and just can't be there. If they are actually not able to be in the building or talking to any other staff members then things break down incredibly quickly.
A lot of the staffs remained in tact at schools that fired their head coach, there's continuity there and sure the head coach is gone, but someone can assume that role and do a just as shitty job as a fired guy.
This is not that, this is half the entire coaching staff and the part of the staff that made Ole Miss prolific is not only physically gone, they also took their playbooks with them, all the resources with them and there is no one left to pick up the pieces and put together a functional strategy or gameplan with the current roster against a team. It's crazy to think that Ole Miss won't just get wildly outcoached in any game and the only advantage they have will be a talent advantage against a shitty G5 team or something.